Our toilet never held water since the day we took delivery of our RW.
I would clean it and it would hold water for a day or so, then back to not holding water for more than 15 to 20 minutes.
Since I cleaned it again a few weeks ago and coated it with the Oatly Plumbers Facet and Valve Grease, it has been holding water just fine.
Robert & Sheryl
2014 Redwood 38FL
MoRyde 8K IS, Disc Brakes, MoRyde Pin Box
17.5 Goodyear G114's, RV Armor Roof
2018 RAM 3500 DRW, Curt Q24 Hitch