Before you do too many double back flips, do a search for poop pyramid and read all about that issue. That is the problem when Mine burps. No big deal to straighten it up with the whirly bird cleaner from Waly world.
As said before,ours burps a little when almost full and that is the last warning we get.This is a new unit and i always do the flush when i'm emptying the tank and i don't rely on the guage.
Thanks again for the replies.
Before the trip, the tank was emptied and flushed. There were 3 of us, and it was only after 6 days that it acted like that. Our gauges have always worked correctly (now I wonder tho...) and we use the geo method. Our tank has the back flush thing in it.
We are going to go dump this weekend, and are going to flush it 2 or 3 times just to make sure, the "pyramid" thing could very well have been the culprit here.