We replaced our PV array last October, due to ongoing production shortfalls. I have not heard the final diagnosis, but it was clear the panels were malfunctioning because they were maxing out at 72% of their rated capacity.
A few months into the new system confirms the magnitude of the problem: the production numbers for November and December were the best ever for this system. January and February tied previous records, and in April this array smoked the previous best by 32%!
The new panels are 130-watt units, which is a small upgrade in theoretical capacity from the previous model (125 watts), but I think the performance gains are due primarily to the fact that the new array isn’t b0rked.