BuildCraft version: 7.99.13
Forge version: 14.23.1.2555
Link to crash report or log: https://pastebin.com/Nm5P0ifq
Singleplayer or multiplayer: Singleplayer (client only)

Try to update CodeChicken Lib.

Yes, I pushed a CCL update weeks ago in order to fix this crash..

Hmm. I tried updating it and now it's a different crash message. Also, of note is the fact that it works perfectly on the server now - only the client crashes.

https://pastebin.com/pyCXuZFb

Try to update Integrated Dynamics.

Thanks very much for the help! That fixed it. I don't know how to close an issue (or even if I can) but it's definitely fixed now.