I had a similar occurance. I thought it was happening because of the
faucet. I never used the city water option and it was always a pain to try
to remember which way to turn the faucet to select the onboard system or
city water. Louise would curse the system. My solution was to add the
GoWesty hands free foot switch. The faucet stays in the internal water
position always. No more fumbling with the faucet with wet hands. I think
the faucet will last longer. The hands free kit is easy to install.
I also removed the city water system and capped it off at the faucet. I
only learned about the check valve later.
I also have to think about adding a fan to the city water panel. Camping
this summer in 30 deg. C. temps and having hot air being pumped in the
cabin from the fridge was brutal!