Here is the crash log:
https://pastebin.com/hBh2Du7S

Is this happening around all butcher houses?

So far, yes. Eventually. Not always right away. The villages are added by Mo' Villages if that makes a difference.

Maybe check for null at this line?

is the mod pack you're using a public one? I've been trying to get it to crash, but it just won't.

Not yet, but here is a link to the exported profile (essentially the modpack) from the Twitch launcher. https://www.dropbox.com/s/m70vy1vwbnf4ojr/Seasons-1.0.zip?dl=0

Note that Animania is in the pack but its config is set to also allow Vanilla animals to spawn.

Make sure and choose the Biomes O Plenty world type. Here is the last seed I was using 8669932344295807619 .

The coordinates for the village that is crashing is x 581 z -36

SAcustombuild.zip
Can you try using this file? I think I've fixed it

Ok. So it crashed when I opened the old world which had SA installed and then uninstalled.

When I created a new world with the seed and visited the village, no crash.. so far. I also notice that in the crash world there were floating carcasses in the shop like with no hanger. But in the new world and build this doesn't happen.

The 2nd village with butcher I found had floating carcasses but no crash.

Alright. I’m not exactly sure why it was crashing, I was accessing the blocks the 1.9 way, but it really shouldn’t have crashed. I’m going to leave this issue open for a week, if you don’t get any more crashes, I’ll close it and push this version to Curseforge.

Carcass’ on the floor have been there since 1.7.10, don’t know why it happens and every time I try and fix it, I cause more issues

Sorry to say.... Crash in new world with expanded pack. I don't think it is mod interactions at this point?

https://pastebin.com/vUnsesKD

This may be because I can’t math. I’ll double check it tomorrow

Still keeping an eye on this. Let me know if you have more builds to test.