Hi Bandarr3000. That's interesting that it happen just near strong signals. I can't really advise on why that is. But as a fellow RSP2 user, I can say that in general I don't find cranking the RF gain to be a lot of help. It could be because of my urban surroundings, which I'm starting to really realize is full of strong broadcast signals that are likely affecting things. I'm not sure that the RSP2pro, the metal cased version which I have, is actually that good at front end interference rejection. I have tons of MW images in the 2-3 MHz range despite the use of a 2 MHz high pass filter, and even if I'm using one of the SMA connections instead of the High Z port. It could be my coax (LMR400) and it could be that I should try to bury it instead of hanging it, but it could be that the SDRplay RSPs, nice as they are, are still limited in some features as you might expect for a product that's as inexpensive as it is. Personally, I would like to see what things for me would be like if I plugged in a higher end SDR but left everything else as is.
Anyway, boosting the RF gain tends to make little difference to increasing the signal, at least to my ears or to the posted SNR, while making unwanted noise slightly worse. So I usually use it only when I'm tuned to a weak signal that can benefit from it, or one of my usually fruitless attempts to decode a DRM signal. I never use it on good signals. So if you're experiencing this ONLY when you boost the RF gain, my suggestion would be to keep it lower, or halfway up at the most.
Good luck!