Error 4 on Baumatic Suprema1w/ss?

Our Baumatic Suprema1w/ss keeps showing error 4. Have tried tip of tipping backwards and forwards but is still happening!
Other tip online of taking off front black covers does not help as we do not appear to have on our model (taken front plinth off).

If anyone can help would be very much appreciated before we take a hammer to it.

Have called out engineers several times but they can not fix it either, costing us call out fee every time!

Many thanks, Jill