Couple thoughts come to mind.
First, as stated above, the hose is holding pressure, (as stated above)
Second, nothing wrong with your pressure regulator.
Third, is your filter clogged up?
Fourth... I quit using water connected to the campground spigot. I attach my hose long enough to fill my fresh water tank on my camper, then run water from the fresh water tank. I run water into the tank via a filter also.
Although I have never had problems with water pressure at any campground (because I have a pressure regulator also)... I quite doing this because of 2 events that happened.
First: When we got our new Outback TT, we stopped at a KOA campground. When we check in, the manager told us to use the regulator because the water pressure through out the entire campground was above 70 PSI, and without a regulator, we'd blow our trailer pipes out! (Oh yuck).
This got me to thinking???? Just how good is that little regulator. So right then I decided to go ahead and fill the fresh tank and not worry about pressure at all. After all, the on board pump is made to be at the right pressure! Right? So I filled the fresh water tank, unhooked the hose, and ran off the tank. I've been doing it that way ever since.
This also prevents the problem of LOW pressure, which we did experiences a lot in our past.
Second. This event happened a few years ago, but it taught me a lesson, to always keep fresh water in the tank. We were at a campground that had their own water supply, on their own well system. We were connected via the hose, happy camping, when sometime in the middle of the night, their pump house had major electrical problems and .... you guessed it ... no water to the entire campground. We were scheduled to be there several days. I will say that next morning, the entire campground (campers) were all in a panic. I did have about 1/3 fresh water tank full, although the water was not recently "fresh" it was enough we could take showers and such in the camper, which we did.
Finally, they got the power problem worked out and the water going again. It took the entire day to get it fixed. I then drained the old water out of the fresh tank, and then refilled with fresh water.
And you know what? Their pump house blew again that second night! Only this time, it took 3 days to get the water going! We were quite comfortable... we had plenty of water in the fresh tank, and we had a marvelous time! But... there were many people in the campground who packed up and left. Before the 3 days was over, there were only a very few of us left.
So between these 2 events, I have always A) filled my fresh water tank when first arriving at a new campsite. B) would hook up the garden hose. But after the KOA incident, I just now fill up the tank and turn the campground spigot off!
May I suggest you do the same and then you don't have to worry about pressure at all. (although you do have to hear the water pump run in your camper, but really, that's not so bad ... really!)