For the most part, I had little trouble with the arm section. But the one thing I can't quite figure out is if I move or rotate the hand or forearm controls, I'm getting bending at the midsections of the bones that aren't supposed to bend. I get it with both the IK and the FK controls, so I feel like the problem is likely in the DEF or MCH or tweaks. I've double checked parenting, locks, constraints and can't figure out what I'm missing. (I have the upper arm shown here... hand does the same, but seems even more extreme in the bending I get on the forearm)
It's kind of hard without looking at the file. My first guess is something with the weights. My second guess would be with the bendy bone settings. My third guess would be multiple armature modifiers.
