So dropping gains right down doesn't stop the oscillations?. Is the naza hardmounted, they don't like vibrations. Maybe in blheli suit try reducing motor timing or turn off damped light? Maybe time for a naze32 or something more suited to miniquads than naza?
I did as you just described above to calibrate the esc's on my last build using a 4 into 1 harness also as same as above pic, then removed rx and setup new serial rx and all esc's stayed calibrated,