That's my world after update

Also having this issue, was very surprised when I logged on :)

This TextureStitchEvent issue is apparently way more severe than I thought.

It is basically caused by other mods registering their textures into a texture atlas used by my mod and they are not supposed to do this. This has no relevant consequences for my mod (it would still work fine) but apparently some of these other mods break all models as a result if it.

There are 2 ways to fix this:

1. The other mod(s) adds a single line of code to their event handler
2. I have to hack the hell out of the TextureMap vanilla/forge code to get it fixed.

Unfortunately I know for sure they won't fix it and just say "but other mods do the same, so I'm right and you are wrong".
Looks like I have to fix it.