Same thing happened here when i was testing my belt grinder, the vfd and the 3kw motor. At the end i had to open the VFD and say "bye bye" to 6 capacitors which were connected to ground. Desoldered them and now all is allright. That with the Siemens micromaster 420. Luckily the Toshiba inverter have a button to lift the capacitors from ground in urban scenario.

To check if that's the case you just check using V meter if you have leak voltage on ground pin. Carefull!