We have a 2008 (2009 Model) 2998 RB Sundance. Absolutely love our 5er. Have been having problems flushing the main toilet. It explodes a large bubble when flushed and the water wont stay in the bowl sometimes. I have run the little plastic "thing-a-ma-jig" around the seal several times, but still, at times the water seeps on through. We also hear a gurgling after flushing. I believe the gurgling and bubble are somehow due to the vent not venting properly. I am constantly having to plunge the toilet. Is anyone else having this problem with their coach? Have not had this problem with the rear bathroom. Any advice would be greatly appreciated.None Happy camping!