Client side crash on power transfer, https://hastebin.com/qoxupiqohe

This specific issue can be solved by wrapping the for loop here in an if statement containing !world.isRemote

Looking at the other classes for the other converters it seems that this issue could crop up there as well

Good catch. That should only be running on the logical server. Fix incoming.

fixed in 1.2.1
Should be available on curseforge in a few minutes.