I've had multiple crashes, usually being java.lang.NoSuchFieldError: HEAD/java.lang.NoSuchFieldError: TRINKET

I can't downgrade because of EnderIO, Thaumcraft, and another mod I forgot needs Baubles 1.5.2.

The mods I had issues with were The One Probe, The Twilight Forest, Silent's Gems, Draconic Evolution, and Thaumcraft.

And once I finally removed all of those, the game crashed on world login.

It sounds to me like you are including a mod which is also including some Baubles files. It should not be doing that. You should remove that mod.

Sorry I can't narrow it down. :(