I'm new to this mod and solving crash reports so I don't know what to do. Please be patient with me if I don't understand what is being said.
https://pastebin.com/93QegAnE

I placed one collapsible block down and it didn't crash the game until a couple seconds later. I've tried using earlier versions of the mod, but I'm running 1.12.2 and it won't show up. I only need this mod for sloped blocks. I would really appreciate the help with solving my issue.

Update:
I recreated my situation and found that using glass on the collapsible block is the reason my game crashed. The entity's existence in the game will continue to crash it unless it is deleted, which I don't know how to do.

I noticed you might be running Optifine: that can create render issues and possibly crashes. I will test this out and see if I can locate the issue.

I can reproduce the issue. I'll try to have a new POC out soon with a fix.