Update

The machine also set an error code on start up indicating that the hand control is not responding. Turned out to be a bad connection at the hand control end. When that error was fixed the error code I05 also disappeared. Either it's a bug in the control program or it is a deliberate programming in order to make troubleshooting a little bit more challenging :devious:
Now remains to find out why the power supply to the servo drives does not start