The machine is grounded.
Everithing is happening when no other equipment is on at the factory.
The strange thing is that 90% of the circumstances, the alarm is happening during or afterwards a toolchange.
I though it might be a spark killer of the motor that brings the umbrella of the tools forward and backward to the spindle, or this motor's brake.
I dont know how to check the spark killer and the brake is supplied ok with 90v when the umbrella motor is moving.

Another thing is that our mains is 410V but the transformer of the machine is 380V. I have already ordered a new tranformer so I would check with 220V and not 234V as is now.
The transformer is a little noisy, at the back side of the machine, and close by is the metal pipe whitch has the x-pulse coder cable inside. I moved the transformer about 0.5m away but still no luck.
The power cables go from the transformer to the machine and back and for some length we have 2 power cables near the metal pipe which has the x-pulse coder inside and the metal pipe which has the y-pulse coder inside.
I have checked DC bus is at the upper limit of DC.
24v is OK
5V is ok

Thanks
Michael