Thanks, I found it in newer Steds (8.9). There was faulty DC/DC converter, already repaired and working fine.
There was another strange fault, A.24.15, fortunately without damage in MCU, which was caused by faulty optocoupler and output transistor in SU's channel b of FM2 rpm encoder. No idea what can be reason of it, but also already repaired.

This fault indicate there is not 24v supply to hydraulic MCU when main contactor K1 is connected. Check 24v supply for this unit.

Regards