After updating to version 4.1 I've noticed that the game proceeds to crash every time I've reloaded the resources. The crash report always seems to deem JEI as the culprit, which I feel links back to Sneed as the newest version started caching JEI. Weirdest issue is when coming back into the world, when using Optifines ability to modify entity models, the entities won't have the correct textures being applied to them. So I have a feeling it is whatever method Sneed is using to cache stuff that is causing the weird crash/failure to load textures correctly when refreshing them.
Crash Report
Full Log File

I've got nothing to do with Optifine's entity model stuff. But yes JEI caching won't work on resource reload just yet, will attempt to fix for next version. A lot of resource reloading is broken in 1.12 across various mods fyi (foamfix: memory leak etc)