So I just I had my first "major" issue with my P3 - which I've had for around a year now. Turned on my machine and I could here the balls popping in the trough but no balls were displayed when I looked at the Under Playfield diagnostics. Sent a support message to Multimorphic and TJ was there with a response straight away with ideas I could check - as I went through these (including over the weekend and different time zone) TJ was there to help with almost instant responses. Eventually he suggested I swap over the rear trough (?) switch controller with the flipper controller board and see if that made any difference.
This is one of the great things about the P3 - many of the boards are universally used for multiple switches so I didn't need a spare pinball machine (like I do with my Williams machines) to swap out a board to test it - I just swap it with another one on the machine and change a few dip switches. Once I did that the flippers started playing up and the balls started detecting fine again. Issue was with the board and Multimorphic are sending me a replacement at no charge. Great service.
btw - if I needed to buy a replacement board it's only $45 - not too bad in the scheme of things.