Dear MB experts,

Mercedes B year 2012 diesel 200 CDI 100 kW
engine 651901
km 240000 - miles 149129

Came in shop because sometimes has no power steering while driving and all lights illuminate on dash when it happens.

Replaced engine battery with corroded terminal.
Also replaced small battery.

All fuses and relay in engine and cabin are ok.

Gave the car to the customer and a couple of days later again no power steering while driving.

Everytime it's here the fault is not present.
Found 1 bad ABS sensor on rear wheel but it's not related with power steering fault.

What should I check?