Came across this trying to put Immersive Railroading into Engineers Life 2 modpack. Isolated crash to being caused by coexistance of IR with Spareparts 0.6.3 Full crash report below in a minimal install of just IR, TrackAPI, UMC and Spare parts

This looks to be exactly the same crash that was seen with quark as per this link https://github.com/VazkiiMods/Quark/issues/2727
I also see reference on curseforge to you fixing a rendering compatibility issue associated with the pulley- perhaps this is something similar

---- Minecraft Crash Report ----
// Daisy, daisy...

Time: 18/04/22 2:12 PM
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
at net.minecraft.client.renderer.tileentity.TileEntityRendererDispatcher.func_228850_a_(TileEntityRendererDispatcher.java:83) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.WorldRenderer.func_228426_a_(WorldRenderer.java:1055) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.GameRenderer.func_228378_a_(GameRenderer.java:608) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.GameRenderer.func_195458_a(GameRenderer.java:425) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_195542_b(Minecraft.java:977) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:607) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(Main.java:184) ~[1.16.5.jar:?] {re:classloading,pl:runtimedistcleaner:A}
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_312] {}
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_312] {}
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_312] {}
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_312] {}
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:51) ~[forge-1.16.5-36.2.34.jar:36.2] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.1.3.jar:?] {}

A detailed walkthrough of the error, its code path and all known details is as follows:
-- Head --
Thread: Render thread
Stacktrace:
at net.minecraft.client.renderer.tileentity.TileEntityRendererDispatcher.func_228850_a_(TileEntityRendererDispatcher.java:83) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.WorldRenderer.func_228426_a_(WorldRenderer.java:1055) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.GameRenderer.func_228378_a_(GameRenderer.java:608) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
-- Affected level --
Details:
All players: 1 total; [ClientPlayerEntity['Valheran'/299, l='ClientLevel', x=-243.50, y=100.00, z=-258.50]]
Chunk stats: Client Chunk Cache: 841, 529
Level dimension: minecraft:overworld
Level spawn location: World: (-240,102,-256), Chunk: (at 0,6,0 in -15,-16; contains blocks -240,0,-256 to -225,255,-241), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
Level time: 36 game time, 36 day time
Server brand: forge
Server type: Integrated singleplayer server
Stacktrace:
at net.minecraft.client.world.ClientWorld.func_72914_a(ClientWorld.java:447) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2031) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:628) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(Main.java:184) ~[1.16.5.jar:?] {re:classloading,pl:runtimedistcleaner:A}
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_312] {}
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_312] {}
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_312] {}
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_312] {}
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:51) ~[forge-1.16.5-36.2.34.jar:36.2] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.1.3.jar:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.1.3.jar:?] {}

-- System Details --
Details:
Minecraft Version: 1.16.5
Minecraft Version ID: 1.16.5
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_312, Temurin
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Temurin
Memory: 1355502272 bytes (1292 MB) / 2183135232 bytes (2082 MB) up to 3817865216 bytes (3641 MB)
CPUs: 8
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx4096m -Xms4096m -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xms256m -XX:+IgnoreUnrecognizedVMOptions
ModLauncher: 8.1.3+8.1.3+main-8.1.x.c94d18ec
ModLauncher launch target: fmlclient
ModLauncher naming: srg
ModLauncher services:
/mixin-0.8.4.jar mixin PLUGINSERVICE
/eventbus-4.0.0.jar eventbus PLUGINSERVICE
/forge-1.16.5-36.2.34.jar object_holder_definalize PLUGINSERVICE
/forge-1.16.5-36.2.34.jar runtime_enum_extender PLUGINSERVICE
/accesstransformers-3.0.1.jar accesstransformer PLUGINSERVICE
/forge-1.16.5-36.2.34.jar capability_inject_definalize PLUGINSERVICE
/forge-1.16.5-36.2.34.jar runtimedistcleaner PLUGINSERVICE
/mixin-0.8.4.jar mixin TRANSFORMATIONSERVICE
/forge-1.16.5-36.2.34.jar fml TRANSFORMATIONSERVICE
FML: 36.2
Forge: net.minecraftforge:36.2.34
FML Language Providers:
[email protected]
minecraft@1
Mod List:
forge-1.16.5-36.2.34-client.jar |Minecraft |minecraft |1.16.5 |DONE |Manifest: NOSIGNATURE
spareparts-1.16.5-v0.6.3.jar |Spare Parts |spareparts |1.16.5-v0.6.3 |DONE |Manifest: NOSIGNATURE
TrackAPI-1.16.4-forge-1.2.1.jar |TrackAPI |trackapi |1.2 |DONE |Manifest: NOSIGNATURE
forge-1.16.5-36.2.34-universal.jar |Forge |forge |36.2.34 |DONE |Manifest: 22:af:21:d8:19:82:7f:93:94:fe:2b:ac:b7:e4:41:57:68:39:87:b1:a7:5c:c6:44:f9:25:74:21:14:f5:0d:90
ImmersiveRailroading-1.16.5-forge-1.9.1.jar |Immersive Railroading |immersiverailroading |1.16.5-forge-1.9.1 |DONE |Manifest: NOSIGNATURE
UniversalModCore-1.16.5-forge-1.1.3.jar |Universal Mod Core |universalmodcore |1.1.3 |DONE |Manifest: NOSIGNATURE
Crash Report UUID: cb438f2f-177d-4fd9-bde6-5b33d5442520
Launched Version: 1.16.5
Backend library: LWJGL version 3.2.2 build 10
Backend API: NVIDIA GeForce GTX 1060 6GB/PCIe/SSE2 GL version 4.6.0 NVIDIA 511.79, NVIDIA Corporation
GL Caps: Using framebuffer using OpenGL 3.0
Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'forge'
Type: Client (map_client.txt)
Graphics mode: fancy
Resource Packs:
Current Language: English (US)
CPU: 8x Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz

Curious. Having looked into it, my experience was a crash on world load. I can't say for certain if the issue is with Spare Parts or IR. Rolling Spare Parts back to the prior version, 0.6.2 seems to fix the issue. Adding IR to the pack is an at your own risk endeavor, but you could try rolling back Spare Parts and seeing if that helps. IR was considered for EL2, but the large number of open issues on their github was a concern. I can understand wanting to add it.

Thanks for having a look. That is the same crash i was getting, just after world load, in both built up worlds and fresh spawn, its a shame there isnt more helpful information. I have raised the issue also on the IR github. Obviously changing the modpack can always have unintended consequences - I have never played with IR before, but it seemed to be a good fit with EL2, and I have a world already fully built up industrially so I thought I'd give it a crack