T200 stator isolation degrading

Hello everybody, I was wondering if anyone has tested the isolation of the stator coating on new and used T200 thrusters?

We are using surfacesupplied power and are experiencing a lot of power cuts due to the safety system on the PSU. Testing the thrusters for leakage enough to trip the safety systems of the PSU takes a really long time and I would like to test them by “megging” instead.

Has anyone tried this? What testing voltage is safe to use? What are acceptable readings? Are you soaking them before and how fast does the coating typically degrade?

My measurement on 100V goes from:
Full isolation dry and unused.
66 Megohm when run for 6 hours
2 Kiloohm when run for 12.
And everything inbetween.

We are running a JM Robotics PSU top-side and the Outland enclosure on the ROV. After running the system for 1300 hours on two ROVs we have replaced 25 thrusters.