I tried to create a new modpack using several 1.12.2 mods, which all worked flawlessly. Only buildcraft proves to be a problem, since the game only crashes with it installed and gives me this weird report:

Ps: Maybe that's just a beta bug and will soon get fixed, in that case thx for your help.

crash-2019-10-08_19.27.15-client.txt

the problem isn't buildcraft in this case. the problem is optifine screwing with the rendering in ways that break BC.

sadly it is extremely hard from the BC side of things to be compatible with optifine since optifine is closed source and we thus have no clue of the full scope of changes it makes to the way minecraft renders

Okay that is a great relief and thank you very very much for the quick answer!
I'll try doing everything without optifine and see if it works.

Ps: But if I still want to use shaders I can just use the shadersmod only am I right?

Does this work with the latest build of buildcraft? I'm using optifine with shaders too and tried with BC 24.4 through 24.6, I've never had a problem with this. Is it still an issue?