I have two arrays for my AC500, and for the second time one of the arrays fried the MC4 connector, leaving burnt black plastic and charred wiring.
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I can only guess that there’s too much electrical resistance at the crimp point inside the MC4, causing the fire. I have the correct crimp tool which gives professional factory looking results. The only thing I can see to fix it is to start soldering all the connections.
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I doubt it’s the weather as we get so little rain that it’s headline news when it happens. We get so few thunderstorms that the Ring Community forum lit up with reports of flashing lights in the sky. “What the hell is that?” We’re just south of Area 51 so I ran outside with my camera, looked around, went back inside and reported, “Uh guys, we call that “lightning” where I’m from.” The thunderstorm was too far away to hear the thunder. 
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Two observations -
- It would help to answer your Q if you noted the Voltage and Wattage you are using through your connectors.
- Not all MC4 connectors are “good” quality. I don’t know what you are using in the U.S. but some cheaper manufactured ones are known for this issue.
It might also help if you noted cable gauge, run length, panel array size and parallel/series connection etc.
Edit, Soldering can increase resistance, MC4 connectors are intended to be crimped, not soldered. Soldering can compromise water resistance and create a weak point. (mechanical stress)
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