The diagnosis has been confirmed

I contacted the seller of the panel and he said it was indeed a used panel. That begs the question as to why it was so expensive but anyway, the situation was amicably resolved and I got my money refunded. I'd buy from him again, since he seems a straight, honest dealer.

Yesterday on my trip to Harbor Freight, I got a couple of things including a 15W solar panel. Now that panel turns out to be much heavier than my faulty panel. Checking the screw holes, they're a bit big for an 8-24 and a bit small for a 1/4-20. I'll have to find something that fits. That's a trip to the hardware store.

As the panel will be supported by solely 4 bolts and the 14 gauge bus skin is quite thin, I need to spread the weight a bit. This means I'll probably end up with two steel strips with bolts welded to them, one for each side of the panel then rivet the strips to the bodywork. I can then fasten the panel with lock nuts.

I posted a photo of the problem areas of the solar panel online. Apparently it looks quite shot. The seller just refunded me and said he didn't want the panel back, that means I now have spare cable and connectors, which is very welcome.

Today was oppressively hot but I managed to reduce what's in the bus and in my car by two very large, very full bags of garbage. I'll try to reduce yet further in the coming weeks while I complete my conversion. Rain had been forecast so I didn't do any further welding nor any media blasting. Tomorrow may be more forgiving.