IRC5 becomes active by itself

Dear All

Today I installed IRB 2400 and everything was normal. But everytime I shutdown the controller, about 20 minutes later, the IRC5 becomes active (turn on) automatically, shown by booting system for few seconds and then becomes turn off by itself. Whereas ON-OFF switch is in OFF position and I have disconnected 3 phase power from the source.
Can anyone explain this strange thing? I predict that there is something wrong with Capacitor (energy) bank.

BR
Dhyan Wicaksono
ABB Robot Programmer