fwiw. had a similar with my 14 Flagstaff 832 IKBS on 1st trip out Had tested (limited, not sustained) city water hookup and good results, but. the check-valve in the pump went south (or was defective). allowed the water to back-feed into the FW tank. which happened to have a loose overflow hose connection and allowed water to run back (outside the overflow hose).. into the trailer. all over bathroom floor under the sink, under the wall over towards BR slide out. and in general make a bit wet mess. New pump fixed things along with tightening that connector to the overflow hose. No problems since. it was under warranty, but in that instance I had to front the cost of the pump and FR paid me back.
that MAY or MAY not be similar to your problem, but might be worth checking.
14 Flagstaff 832IKBS/Platinum
pulled by 07 GMC 2500HD/Duramax CC 4x4 with a ranch hand bumper, hadley air, piaa fogs, topper w/rack and a bed-slide!
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