Lets try to stay with as few threads as possible so it’s easier to follow this.
Regarding this thread I’d say check the gain, either overloaded or some interference would be my guess.
Knowing nothing more of your complete setup nor what experience level you are, here goes.
There’s a few threads on the setting gain topic, as well as a bit down in the Omnidirectional_Station_How_To.
Using too low or too high gain leads to reduced signal to noise ratio and in the too high scenario leads to a lot of other odd artifacts as well.
RX chain, basically it boils down to keeping RFI from the antenna (and antenna away from the sources), good placement, grounding and RF chokes on the coax. The antenna needs to be designed properly, when browsing the net and stumbling on pictures like this
I’d say the “optional” part with the balun is not true, at least use some chokes or the simple coax coil close to the feedpoint.