Posted about this prior on my 2016 forest river Cherokee 265b. Was told to check the hose routing and the vent tube. Today I pulled the belly panel off my trailer and had a look. Vent tube I removed completely and it was perfectly clear, from what I could see of the fill hose it looked fine with no low spots or kinks.

While I have yet to try filling the tank, I think the issue is still present because if I use my mouth to blow air into the fill port, as soon as I remove my mouth I can hear/feel air coming back out of the fill port. Any ideas what else it could be before I take it to a dealer?

We generally camp at state parks without hookups so having a fresh water source for washing up is needed.

EDIT: YES I REMOVED THE VENT HOSE AND THE FITTING AT THE TANK, IT IS CLEAR. I put it in all caps so maybe some of you would read it this time.