I used to install 100's of solar edge system , now if you go into your portal you should have a icon called charts IF ONLY your installer set you up as an advanced user, you can check graphs such as voltage, AC & DC currents etc etc for each panel. this may give you more ideas. a PO cost about £35 ex VAT so that is the cheapest solution. or swap OA around see if when you swap one for the faulty one does the panel with the suspected faulty OA start to under perform , The big problem is roof access I guess ... if it was me I would just max the life out of the panel and when it does start to make a big loss then get a panel that looks similar and swap it. you can mix and match panels with solar edge. upgrading the firmware from solar edge wont do anything or repairing them to the system.