I have a 2018 NL 8-11, every now and then I get that as well and I have had that happen is just about every RV I have owned. Usually “ I have found” that there is a water valve kitchen sink, bathroom, sink, outside shower... one of those taps is open just enough so that when the system is pressurized, the air will slowly escape and the pump has to re pressurize the system, you won’t see any water... it’s just air escaping they by the system won’t stay pressurized very long. I found the outside shower tap just cracked every so slightly a few times. Most time when you check them to ensure they are closed 100% you won’t even notice the movement it is so slight.
I’m not saying this is your issue, but check everything that is on the water system to make sure it is closed and tight, even the fill cap for the fresh water tank.
Good luck
Soup.
