Front seats intermittently (not) working

[yejee]

Hi all
I have an annoying issue with my MB. Drivers seat most of time (!) doesn't move forwards and passengers seat doesn't sometimes (!) move backwards. All other movements work perfectly all the time.
I'd rule out switches on doors, since I can hear a relay clicking in a black box under seats when I press button. This should mean that black control box and wiring is fine?
I've taken both seats out and cleaned and greased the rails. I also took the motors apart and cleaned them. They looked visually good as new including brushes. If I used battery and tested motors on table out of car they worked fine.
So I'm bit confused why the seats are not working. Any one here have some experience with this or can point out some test what would tell which part is gone bad?
Cheers

 

[richard]

There are sensors in the seats too. The seat controllers will report faults (stuck motors etc), so if you get it on Star Diagnosis it will tell you what is most likely wrong - and using actuations and actual values menus in Star you can work out what is wrong if the fault code logging isn't as expected

Cheers

Richard