My neighbour has the same panels but never looks at the output. I told him to check them and he was shocked. How many others are there they simply don't check the output and keep spouting that panels have multi decade lifetimes.
It was so significant that one of the 2 strings, 6 panels each, simply shut off especially during peak hours because the inverter's minimal input voltage wasn't met (during peak voltage usually drops due to negative heat coefficient). 1 simply was broken and was bypassed by the.. bypass diodes i guess. And another was at a third. But again, the lower voltage was a much bigger problem than the input.
problem is, you can only measure this very well under load. So taking your multi meter to the place of sale might not say that much. `It might though for the really broken ones.