I had some problems with my processor recently. I noticed that
1) When it's pretty hot (we've had a long hot summer in Malta this year!) the volume seems to go down quite substantially. When I tried auxiliary cables the sound was fine so it was related to the microphones. When temperatures went down, I heard a sort of pop and everything went fine. What I also noticed was that this volume reduction seemed to be 'announced' by a rustling sound similar to the one that you move a cloth against a microphone.
2) I also noticed that, at times, when I switch the processor on, it turns itself off again, then when I turn it back on again, it seems to loop between the Sensitivity settings and the volume. Pressing the sensitivity button seems to lead it to 'hanging' as the on switch doesn't work. The only way to reset is to remove the battery compartment and put it in again.
I reported it to the Manchester CI centre and in their typical efficiency they sent me a new controller, even putting a self addressed padded envelope in for me to send my existing one back - apparently the second problem is a known one. I'm currently with another controller and seeing what happens.