When it comes to cable TV at campgrounds not all are created equal. Some may still supply only an analog signal and some supply digital (or maybe both).
I have noticed my newest LED TV does not work the same as the old on some cable systems used in the past.
The best answer is to carry a coaxial cable long enough to put through a window or door and connect directly to your television, instead of connecting to outside plate on the RV (instead of using internal coaxial circuit). I have found this method works best.
Since the other way will still work the regular way at some locations, I have given up thinking there is anything wrong with the internal circuit. The signal put out by the campground may be degraded too much by following the usual route.
Don't forget to leave the roof antenna amplifier turned off. Any signals entering that way can interfere with the cable signal.