I had the same problem with our rear view camera. I sourced a new camera then learned on our coach the connection is buried inside the rear fascia and cannot be accessed without removing the fascia.
So I pulled the radio out and connected the new camera directly to it to see if the radio was the problem. New camera had a crystal clear picture, so I reconnected the cables and put the radio back in. There was a three foot "pigtail" cable between the radio and the cable that run to the rear with RCA connectors too.
Like magic, the rear camera began working perfectly again and has worked all last year. I suppose I got lucky and only had a lose or oxidized connection on the radio plugs. I'll just hang on to the new camera for now. Might find a use for it somewhere...
2018 Sunstar 32YE
2 dogs, Max & Bitty