Game crashes everytime I try to use skyhook.

Forge 14.23.5.2808
IE 0.12-88

https://pastebin.com/azZfJXXU

oooookay "concurrent modification" inside the sound system ... that's odd ... can you try without optifine for test?

Okey

Seems that it happenes only with optifine

can you open an issue over there and link it here? maybe it's something that IE does that makes the optifine modified classes crash stumble

I experienced this today as well (and similarly was taken aback by the concurrent modification exception in the sound subsystem), but unlike the original submitter of this issue, I do not have optifine.

https://gist.github.com/esotericist/03c2e132982d0ce735da634e81d4b17c

in your case i would suggest a test without foamfix and randompatches, but only on a fresh world. Maybe foamfix does something similar with the sound system and i could not find out what randompatches is but it patches quite a few classes