Daikin VRV REMQ16PY1+REMQ10Py1 --> E5 fault

got a site with half a dozen vrv systems, all hooked up to a bms and a daikin central controller.
one of the systems has been giving an intermittent E5 error and changing the fan coils from cooling mode to fan mode.

the tech managed to see it play up while on site. (obviously the part load demands would only bring the inverter compressor in at certain times)
the master unit attempted to start the inverter compressor and then produced fault code after 3 attempts.
the inverter board of the master unit (remq16py1) was reportedly giving voltage intermittently when trying to start the compressor.
checked the diodes of the inverter board, found some to be out of range.
the tech checked the insulation resistance of the compressor and the resistance of the windings, ok.

both compressors in the slave run ok.

the tech has replaced inverter board in the master, which is a revised board (different to the factory original), and new wiring harnesses.

the inverter compressor tries to start but the run amps jump all over the place apparently and then trips out on E5 again.
the tech didn't check the voltages coming out of the inverter board.

what advice do you vrv gurus have that I can give to my tech?
what voltages should he expect out of the inverter board?

is there anyway to test the compressor mechanically? can we hot wire it? (3phase ac compressor, what if we ran it dol to test it spins?)
hook it up to one of the other systems? etc?

You can't test the compressor mechanically. Test the output voltages of the inverter Board.All voltages should be the same , i.e balanced. If a new Inverter board was fitted and the running amps are all over the place it sounds like the compressor is seized.