Plain wireguard. Or maybe Pangolin?

https://github.com/fosrl/pangolin

Apart from the already mentioned possible causes, it could be temperature: digital camera sensors (e.g. in cellphones) are very sensitive to heat, and I’ve had a couple of badly designed devices where the heat gets too close to the sensor. The result are photos similar to yours, specially noticeable in low light (though mine were more purple-ish than green/blue).