Nobody knows? Big Problem with 20/50 Failure 119

Hi to all!
I do have a 20/50 which is working for usual
But does have the problem since about 1 week
So the miller is in the workpiece with about 2900rpm and 0.2mm- Then just goes down to 0.035mm, then stops and shows alarm 119.
Only in Automatic mode is the problem. Tried to change some boards but without luck (didn´t changed all boards).

When alarm comes there is no failure on spindle drive or axis amplifier.

Sometimes the machine also is running 3 hours without any failure.
Maybe someone does know what up with the machine.
Thanks a lot!