There is a "rubber cone washer" in the female end of the water connection fitting that screws to the toilet flush valve. If that rubber cone washer is deformed or damaged, water can leak past it to the threads and drip onto the floor.
It "could be" as simple as a "deformed cone washer that seals with 40 PSI but leaks at 50 PSI"... throughout the day, depending on water use in the campground, the water pressure will change, sometimes "DRAMATICALLY"....
One campground we visit in Marquette MI has water pressure during the day that's around 60-80 PSI and at night can creep up to well over 130 PSI. There's an industrial complex that primarily works "day shift" located next to the campground. When they close and stop using water, the pressure in that entire part of town increases....
If you don't have one, you might want to consider a "real water pressure regulator" (not a water volume restrictor)....
Here's one example of what a pressure regulator is:
https://www.amazon.com/RVGUARD-Press...NsaWNrPXRydWU=
And a couple of "what NOT to buy":
https://www.amazon.com/Hourleey-Hi-F...%2C200&sr=8-41
https://www.amazon.com/Hourleey-Pres...s%2C200&sr=8-8