Hi,
Overvoltage faults are usually problems with the dynamic braking resistors either being open or not sized properly for the job. Empty car up or full load down generates voltage back to drive. Drive dumps excess into DBR bank. if there was no vibrations prior to adjusting inertia, call Mag to properly size resistors and put inertia back to original settings. If vibration was there originally, look to remove springs from CW side of cables if you have springs on both sides.

Best of luck to ya!
Ny guy