Strange Solar drop

[WondaHero]

So I've got two 39-watt Sunbeam panels wired in parallel to a Victron MPPT. After three seasons of solid performance, I noticed a big drop in output. Testing showed each panel seems fine solo, but when I reconnect the port and starboard panels in parallel, output drops to nearly nothing. It's behaving more like a series setup, so I am here wondering if anyone seen this before?

 

[HanSoloBerger]

Sounds like a potential wiring issue or some corrosion. Best to triple check all junctions, connectors, and fuses, especially where the panels join in parallel. Confirm the polarity on both panels, a reversed connection could explain the drop in output. Also, a bad Y-connector that's creating high resistance or even causing the panels to backfeed each other. Hope this helps

 

[WondaHero]

I'll double-check all connectors, polarity, and the Y-connector for corrosion or damage