Just dealt with this myself. I bought my trailer July of 2019, and since there was a pandemic and parks were closed, I think we only went out once in 2020, so it sat parked the entire time. 2021 we didn't take any long trips as well. So the trailer has spent it's life parked with the exception of the first 6 months of owning it... We took a trip to New Mexico and Colorado. I called Furion and asked if there was anything they could do, but it was outside of warranty. I asked if they could send me a different lens as I believed the lens to be the issue, and the answer was no. Well.. When you're outside of warranty and they refuse to do anything, that's when I start being creative and attempting to do whatever I can to fix it.
I tried cleaning the lens and it continued to look dirty, I couldn't see anything when I connected to the camera the picture was too poor to make anything out. I took the camera off the back of my RV, and examined it. Internal moisture will appear as beads and bubbles on the inside of the lens. This is not what my issue was.
I believe thier lens material (plastic) has a UV issue and that it fogs or develops what looks like a cataract after being exposed to sunlight after a period of time. This is just my thought, but I'm going to put a hood onto my camera when parked so the lens won't be exposed to direct sunlight. I'm willing to bet this will extend the life of the lens by quite a bit. If you can afford to build an environmentally controlled garage for your trailer, that would be the best way to preserve your investment.. I'm not rich, or I would have just chucked this camera and bought a new one. I'm an engineer, so that means I make other people rich and suffer poor design choices in what I buy.
I removed and disassembled the camera. The lens is a tube that is weather sealed. I didn't attempt to take it apart since there wasn't a moisture issue, the weather seal is good and intact. If you don't have a sealing issue, I wouldn't recommend taking it apart, the tube could be filled with nitrogen or some other inert gas to keep it clear from condensation. You could take the time to reinforce the weather seal by just lapping some good silicone sealant ontop of theirs.. won't hurt it.
After removing the lens tube I applied sewing machine oil to 3000 grit sand paper and ground the lens in a circular pattern with my index finger. I took a photo before and after and I noticed a significant improvement to the clarity of the lens.
Reassembled the lens and put it back on the RV. I trailiered up Thursday for a trip and I took a look to see how much of an improvement it was. The picture looked as good as it did when I first bought it.
I would have posted pictures, but my cell phone recently died.. I ordered parts for it, so hopefully I'll have something in the future.