Ok, time for an update.

Just tried switching pretty much every part around on the motors. Switched out rotors, switched out sensor boards, switched out sensor cables. I've got basically 2x Revtechs and sensor cables and rotors. I've tried every combination of all the parts. Rotor A with Sensor Board A with Sensor Cable A. Rotor B with Sensor Board A with Sensor Cable A, etc etc etc...

Still nothing. It does the same crap as always. Now, I did notice that the first time I fixed it, it had something to do with the sensor cable. Is it possible that I just have absolutely rotten luck and both of the sensor cables I have are faulty? that seems pretty harsh, especially if I just spent the whole night figuring this out...