Toilet fill head scratcher....
We've got a 2019 27FB Globetrotter with a Dometic toilet.
Most of the time when I slightly depress the flush valve, the fill water immediately comes out of the gallery holes to spin water into the bowl to fill it. However, if the toilet hasn't been used for a few hours, it takes 4 or 5 seconds for the water to begin the fill. There's the white tube coming up from the flush valve to introduce water into the gallery around the top of the toilet rim. I'm guessing that the 4 or 5 seconds is the time it takes to fill the tube and the gallery.
What's got me stumped is how that tube and/or gallery got emptied since the last flush. There doesn't appear to be any leaks around the toilet, or beneath the rig, but if it were a leak it would have to be inside the camper and above the flush valve, unless somehow that water bleeds back through the valve into the pressurized side.
I do believe that one time, we were in a camp site with extremely high water pressure (I blew up an external filter to prove it), but it seemed like the fill water was always immediately available. We do have the standard built in internal pressure regulator.
It's not a major problem, but for some types of people.... we just can't let go of something once we start to chew on it.