Some reported a main output issue but it was a while ago and unclear which mixer model. Maybe there's something in that thread to help you resolve the problem.

Cheers Mr Switchback
I'll try a re flash first and see if I get any joy from that.
It's a pity Presonus don't do a one price fix in the UK like they do in the States?

I think it's great that there is not one price for anything, because repairs can be very different. Here in Germany the procedure is that after shipping the mixer to the distributor you get a note about what has to be done and how much repair and shipping back will cost. If you pay the bill, the repair is done immediately. If it is only a single fader bank that went south, a repair should not cost much. The fader in the classic series had some constructional problems, which were solved with the AI series.