I have not experienced this issue with any of the V19 versions.
When entering the drivers seat of any operable vehicle (any car pack) causes the game to crash. this happens in all of the most recent versions of V20.

here is what it tells me at first:

The game crashed whilst ticking entity
Error: java.lang.ArrayIndexOutOfBoundsException: -1
Exit Code: -1

I have used Vanillafix to see into it more, and says it is a MTS issue.

I will need a crash report to further look into this.

here you go

Time: 1/11/22 2:12 PM
Description: Ticking entity

java.lang.ArrayIndexOutOfBoundsException: -1
at org.lwjgl.input.JInputController.isButtonPressed(JInputController.java:191)
at minecrafttransportsimulator.mcinterface.InterfaceInput.getJoystickButtonValue(InterfaceInput.java:286)
at minecrafttransportsimulator.systems.ControlSystem$ControlsJoystick.isPressed(ControlSystem.java:682)
at minecrafttransportsimulator.systems.ControlSystem.controlBrake(ControlSystem.java:126)
at minecrafttransportsimulator.systems.ControlSystem.controlGroundVehicle(ControlSystem.java:382)
at minecrafttransportsimulator.systems.ControlSystem.controlVehicle(ControlSystem.java:72)
at minecrafttransportsimulator.entities.instances.AEntityVehicleB_Rideable.updateRider(AEntityVehicleB_Rideable.java:100)
at minecrafttransportsimulator.entities.instances.EntityVehicleF_Physics.updateRider(EntityVehicleF_Physics.java:26)
at minecrafttransportsimulator.mcinterface.BuilderEntityExisting.func_184232_k(BuilderEntityExisting.java:235)
at net.minecraft.entity.Entity.func_70098_U(Entity.java:2020)
at net.minecraft.entity.EntityLivingBase.func_70098_U(EntityLivingBase.java:2489)
at net.minecraft.entity.player.EntityPlayer.func_70098_U(EntityPlayer.java:461)
at net.minecraft.client.entity.EntityPlayerSP.func_70098_U(EntityPlayerSP.java:1022)
at net.minecraft.world.World.func_72866_a(World.java:1991)
at net.minecraft.world.World.func_72870_g(World.java:1958)
at net.minecraft.world.World.func_72866_a(World.java:2056)
at net.minecraft.world.World.func_72870_g(World.java:1958)
at net.minecraft.world.World.func_72939_s(World.java:1762)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1847)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1098)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Client thread
Stacktrace:
at org.lwjgl.input.JInputController.isButtonPressed(JInputController.java:191)
at minecrafttransportsimulator.mcinterface.InterfaceInput.getJoystickButtonValue(InterfaceInput.java:286)
at minecrafttransportsimulator.systems.ControlSystem$ControlsJoystick.isPressed(ControlSystem.java:682)
at minecrafttransportsimulator.systems.ControlSystem.controlBrake(ControlSystem.java:126)
at minecrafttransportsimulator.systems.ControlSystem.controlGroundVehicle(ControlSystem.java:382)
at minecrafttransportsimulator.systems.ControlSystem.controlVehicle(ControlSystem.java:72)
at minecrafttransportsimulator.entities.instances.AEntityVehicleB_Rideable.updateRider(AEntityVehicleB_Rideable.java:100)
at minecrafttransportsimulator.entities.instances.EntityVehicleF_Physics.updateRider(EntityVehicleF_Physics.java:26)
at minecrafttransportsimulator.mcinterface.BuilderEntityExisting.func_184232_k(BuilderEntityExisting.java:235)
at net.minecraft.entity.Entity.func_70098_U(Entity.java:2020)
at net.minecraft.entity.EntityLivingBase.func_70098_U(EntityLivingBase.java:2489)
at net.minecraft.entity.player.EntityPlayer.func_70098_U(EntityPlayer.java:461)
at net.minecraft.client.entity.EntityPlayerSP.func_70098_U(EntityPlayerSP.java:1022)
at net.minecraft.world.World.func_72866_a(World.java:1991)
at net.minecraft.world.World.func_72870_g(World.java:1958)
at net.minecraft.world.World.func_72866_a(World.java:2056)
at net.minecraft.world.World.func_72870_g(World.java:1958)

-- Entity being ticked --
Details:
Entity Type: mts:mts_entity (minecrafttransportsimulator.mcinterface.BuilderEntityExisting)
Entity ID: 43
Entity Name: entity.mts_entity.name
Entity's Exact location: 378.34, 22.44, 506.81
Entity's Block location: World: (378,22,506), Chunk: (at 10,1,10 in 23,31; contains blocks 368,0,496 to 383,255,511), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0.00, 0.00, 0.00
Entity's Passengers: [EntityPlayerSP['AugPinochet73'/41, l='MpServer', x=378.89, y=21.96, z=509.11]]
Entity's Vehicle: ERROR NullPointerException: null
Stacktrace:
at net.minecraft.world.World.func_72939_s(World.java:1762)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityPlayerSP['Boeing172'/41, l='MpServer', x=378.89, y=21.96, z=509.11]]
Chunk stats: MultiplayerChunkCache: 3249, 3249
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: World: (796,4,-118), Chunk: (at 12,0,10 in 49,-8; contains blocks 784,0,-128 to 799,255,-113), Region: (1,-1; contains chunks 32,-32 to 63,-1, blocks 512,0,-512 to 1023,255,-1)
Level time: 20342044 game time, 15654 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 58 total; [EntityPlayerSP['AugPinochet73'/41, l='MpServer', x=378.89, y=21.96, z=509.11], BuilderEntityExisting['entity.mts_entity.name'/132, l='MpServer', x=332.25, y=21.15, z=317.75], EntityPainting['Painting'/157, l='MpServer', x=319.00, y=25.00, z=419.03], EntityPainting['Painting'/157, l='MpServer', x=319.00, y=25.00, z=419.03], EntityPainting['Painting'/170, l='MpServer', x=361.00, y=53.00, z=423.97], BuilderEntityExisting['entity.mts_entity.name'/43, l='MpServer', x=378.34, y=22.44, z=506.81], EntityPainting['Painting'/171, l='MpServer', x=355.03, y=52.50, z=424.50], EntityPainting['Painting'/172, l='MpServer', x=345.97, y=25.00, z=446.00], EntityPainting['Painting'/173, l='MpServer', x=362.00, y=34.50, z=544.03], EntityPainting['Painting'/174, l='MpServer', x=357.50, y=34.50, z=549.97], EntityPainting['Painting'/69, l='MpServer', x=268.00, y=30.50, z=363.03], BuilderEntityRenderForwarder['entity.mts_entity_renderer.name'/2619, l='MpServer', x=378.89, y=23.04, z=509.94], BuilderEntityExisting['entity.mts_entity.name'/2620, l='MpServer', x=378.89, y=21.96, z=509.11], BuilderEntityExisting['entity.mts_entity.name'/66, l='MpServer', x=207.00, y=15.63, z=328.00], EntityPainting['Painting'/69, l='MpServer', x=268.00, y=30.50, z=363.03], EntityItemFrame['entity.ItemFrame.name'/70, l='MpServer', x=253.03, y=127.50, z=505.50], EntityItemFrame['entity.ItemFrame.name'/71, l='MpServer', x=253.03, y=127.50, z=503.50], EntityPainting['Painting'/81, l='MpServer', x=274.97, y=30.50, z=367.50], EntityItemFrame['entity.ItemFrame.name'/72, l='MpServer', x=253.03, y=126.50, z=503.50], EntityItemFrame['entity.ItemFrame.name'/73, l='MpServer', x=253.03, y=126.50, z=505.50], BuilderEntityExisting['entity.mts_entity.name'/74, l='MpServer', x=260.05, y=160.12, z=504.67], BuilderEntityExisting['entity.mts_entity.name'/203, l='MpServer', x=377.83, y=22.50, z=322.15], EntityItemFrame['entity.ItemFrame.name'/205, l='MpServer', x=399.50, y=8.50, z=368.97], EntityPainting['Painting'/173, l='MpServer', x=362.00, y=34.50, z=544.03], EntityItemFrame['entity.ItemFrame.name'/206, l='MpServer', x=399.50, y=9.50, z=368.97], EntityPainting['Painting'/174, l='MpServer', x=357.50, y=34.50, z=549.97], BuilderEntityExisting['entity.mts_entity.name'/207, l='MpServer', x=396.00, y=22.44, z=532.00], EntityPainting['Painting'/172, l='MpServer', x=345.97, y=25.00, z=446.00], BuilderEntityExisting['entity.mts_entity.name'/208, l='MpServer', x=378.00, y=21.22, z=551.00], EntityPainting['Painting'/81, l='MpServer', x=274.97, y=30.50, z=367.50], EntityPainting['Painting'/170, l='MpServer', x=361.00, y=53.00, z=423.97], EntityPainting['Painting'/171, l='MpServer', x=355.03, y=52.50, z=424.50], EntityBat['Bat'/83, l='MpServer', x=299.54, y=16.68, z=514.70], EntityItemFrame['entity.ItemFrame.name'/87, l='MpServer', x=281.50, y=127.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/88, l='MpServer', x=280.50, y=127.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/89, l='MpServer', x=279.50, y=127.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/90, l='MpServer', x=280.50, y=128.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/91, l='MpServer', x=281.50, y=128.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/92, l='MpServer', x=282.50, y=128.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/93, l='MpServer', x=281.50, y=129.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/94, l='MpServer', x=280.50, y=129.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/95, l='MpServer', x=282.50, y=129.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/96, l='MpServer', x=279.50, y=128.50, z=502.97], EntityItemFrame['entity.ItemFrame.name'/97, l='MpServer', x=279.50, y=129.50, z=502.97], EntityBat['Bat'/102, l='MpServer', x=301.34, y=22.06, z=498.41], EntityBat['Bat'/103, l='MpServer', x=302.40, y=17.70, z=508.10], EntityBat['Bat'/106, l='MpServer', x=301.88, y=15.16, z=511.28], EntityBat['Bat'/107, l='MpServer', x=303.02, y=18.26, z=509.09], EntityBat['Bat'/108, l='MpServer', x=299.67, y=15.12, z=508.23], EntityBat['Bat'/109, l='MpServer', x=299.49, y=17.77, z=508.84], BuilderEntityExisting['entity.mts_entity.name'/114, l='MpServer', x=315.00, y=22.44, z=272.00], BuilderEntityExisting['entity.mts_entity.name'/248, l='MpServer', x=416.33, y=22.65, z=272.80], BuilderEntityExisting['entity.mts_entity.name'/249, l='MpServer', x=431.94, y=22.54, z=314.23], EntityItemFrame['entity.ItemFrame.name'/250, l='MpServer', x=401.50, y=8.50, z=368.97], EntityItemFrame['entity.ItemFrame.name'/251, l='MpServer', x=400.50, y=8.50, z=368.97], EntityItemFrame['entity.ItemFrame.name'/252, l='MpServer', x=400.50, y=9.50, z=368.97], EntityItemFrame['entity.ItemFrame.name'/253, l='MpServer', x=401.50, y=9.50, z=368.97], EntityArmorStand['Armor Stand'/254, l='MpServer', x=407.50, y=32.06, z=525.50]]
Retry entities: 0 total; []
Server brand: fml,forge
Server type: Integrated singleplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:420)
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2741)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:419)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

Are you using a joystick currently?

yes. I have just figured that out now. everything works without it.

Ah, so your bug is the same as #1033. There's a beta on Discord that will fix this issue. I'm going to mark this as a duplicate of the other bug and close it.