The 1.12 version crashes because you're using the old Redstone Flux API.

https://pastebin.com/1pPcBJ8M

The bug will be solved in tinker_io-1.12-beta 2.5.3f

Before I change the energy system from RF to Forge Energy, we need to install Redstone Flux to provide the energy interface for "Ore Crusher " and "Stirling Engine".

Thanks for reporting!

I have the same crash
https://pastebin.com/tt6wnUTC