Here's the info I got:
-Both Normal Chests and Charset Chests can have locks applied to them while sneaking.
-(Edit: While not sneaking) Normal chests can be opens with keys and the lock in hand. The Charset Chests cannot.

Log info:

[05:54:18] [main/FATAL] [net.minecraft.client.Minecraft]: Unreported exception thrown!
java.lang.NoClassDefFoundError: pl/asie/charset/lib/utils/MultipartUtils
at pl.asie.charset.module.storage.chests.TileEntityChestCharset.isBlocked(TileEntityChestCharset.java:231) ~[TileEntityChestCharset.class:?]
at pl.asie.charset.module.storage.chests.TileEntityChestCharset.activate(TileEntityChestCharset.java:282) ~[TileEntityChestCharset.class:?]
at pl.asie.charset.module.storage.chests.BlockChestCharset.func_180639_a(BlockChestCharset.java:140) ~[BlockChestCharset.class:?]
at net.minecraft.client.multiplayer.PlayerControllerMP.func_187099_a(PlayerControllerMP.java:423) ~[bsa.class:?]
at net.optifine.override.PlayerControllerOF.func_187099_a(PlayerControllerOF.java:96) ~[PlayerControllerOF.class:?]
at net.minecraft.client.Minecraft.func_147121_ag(Minecraft.java:1578) ~[bib.class:?]
at net.minecraft.client.Minecraft.func_184117_aA(Minecraft.java:2253) ~[bib.class:?]
at net.minecraft.client.Minecraft.func_184118_az(Minecraft.java:2019) ~[bib.class:?]
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1807) ~[bib.class:?]
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1097) ~[bib.class:?]
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:397) [bib.class:?]
at net.minecraft.client.main.Main.main(SourceFile:123) [Main.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_181]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_181]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_181]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_181]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
Caused by: java.lang.ClassNotFoundException: pl.asie.charset.lib.utils.MultipartUtils
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_181]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_181]
... 18 more
Caused by: java.lang.NullPointerException
[05:54:20] [main/INFO] [STDOUT]: [net.minecraft.init.Bootstrap:func_179870_a:553]: ---- Minecraft Crash Report ----

WARNING: coremods are present:
CharsetPatchCore (CharsetPatches-0.1.6.jar)
AppleCore (AppleCore-mc1.12.2-3.1.3.jar)
CTMCorePlugin (CTM-MC1.12.2-0.3.2.18.jar)
SCFMLCorePlugin (StalkerCreepers-1.12.1.jar)
TheBetweenlandsLoadingPlugin (TheBetweenlands-3.3.11-core.jar)
TransformerLoader (OpenComputers-MC1.12.2-1.7.2.67.jar)
SmoothWaterCore (SmoothWater-0.1.4.jar)
Narrator Hotkey Disabler (rebindnarrator-1.0.jar)
SSLoadingPlugin (SereneSeasons-1.12.2-1.2.3-universal.jar)
llibrary (llibrary-core-1.0.8-1.12.2.jar)
ComfortsCoreLoadingPlugin (comforts-1.12.2-1.2.0.jar)
IELoadingPlugin (ImmersiveEngineering-core-0.12-84.jar)
Contact their authors BEFORE contacting forge

// Shall we play a game?

Time: 8/15/18 5:54 AM
Description: Unexpected error

java.lang.NoClassDefFoundError: pl/asie/charset/lib/utils/MultipartUtils
at pl.asie.charset.module.storage.chests.TileEntityChestCharset.isBlocked(TileEntityChestCharset.java:231)
at pl.asie.charset.module.storage.chests.TileEntityChestCharset.activate(TileEntityChestCharset.java:282)
at pl.asie.charset.module.storage.chests.BlockChestCharset.func_180639_a(BlockChestCharset.java:140)
at net.minecraft.client.multiplayer.PlayerControllerMP.func_187099_a(PlayerControllerMP.java:423)
at net.optifine.override.PlayerControllerOF.func_187099_a(PlayerControllerOF.java:96)
at net.minecraft.client.Minecraft.func_147121_ag(Minecraft.java:1578)
at net.minecraft.client.Minecraft.func_184117_aA(Minecraft.java:2253)
at net.minecraft.client.Minecraft.func_184118_az(Minecraft.java:2019)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1807)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1097)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:397)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: pl.asie.charset.lib.utils.MultipartUtils
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 18 more
Caused by: java.lang.NullPointerException

Lib/Chests version mismatch