It might be worth a look inside, rubber gloves and extreme care around the caps though!
I've always regarded VFDs as a "Black Box" solution but when I recently had an unexplained bang/flash incident with a 750W Siemens inverter drive which then presented errors I decided it was worth a look.
When I stripped it I found a flexible power link between two internal boards had blown but the motor metered out fine and there were no wiring faults or other visible signs of shorts or damage, it had been running for months without any problem before it blew so I assumed the fused power link was a symptom rather than the fault but in desperation I made & fitted a new link and it's been working fine ever since,
Regards,
Nick