I was able to experience that same problem the other night. I have in a rustler, stock AM rx, MM 6900, CC BEC, but a cheapo 8 cell tenergy nimh pack that had been charged 2-3 weeks prior. 2s or 3s lipo there is no problem. So a deadish 8 cell would cause it. Also, my lvc was set to auto lipo and it recognized the 8 cell as a 3s. So I don't know if perhaps it was bouncin off the lipo cut off or not. I was geared pretty high too. Perhaps it is a battery thing with you.

Just read the rest of your post. Maybe it is just wires interfering. Direct soldering the motor wires and twisting them has done wonders for me.