Replace bad code with more bad code. I should know not to post before testing but not much time to get things done right now. It turns out that moving the low output voltage code to the main run loop just made things worse. Low voltage conditions are a regular occurrence during the MPP scan. So I got rid of that diagnostic entirely. It was there mainly as a HW safety check and as this shows it doesn't contribute.
In its place I added a check for over-current. Originally I opted to skip this since I didn't intend to conscript this into any kind of regular service - and it uses current mode control which is built-in protection. But when the PV panel has high potential a short in the switching core or output might create a hazard.
Yesterday's code has been updated.