Cctvision1

Hi all, I have a DVR hikvision wired up to 3 Dome cameras and 1 PTZ all of which are hikvision and I get a constant message at randomly popping up in the screen saying “the channel does not exist” why am I getting this as I can access all my cameras and there is no issue with anything else so why this message, it pops up at random times could be 5 mins or 20 mins later. I am using a proper Dell monitor and all my firmware is upto date, any help will do