Your most recent failure sounds like the RT battery failed so the board needs to be reflashed.

I wouldn't expect the axis issue from your diagnostics failure because your machine can not run if all diagnostics don't pass. However, since the RT board is what controls all axis motion, I suppose there is some possibility they could be related.

Do you run coolant? Is there a chance your waycovers are letting coolant through to your X-axia servo motor. Fluid infusion can definitely cause issues with the motor, and resolver.