There is a recalibration you can do to get things back to level. Ours was out by about half a bubble - with the level up off - 10 clicks on the front button, 10 clicks on the rear button - manually level - press return and you are good to go.
Like Ducky, I too had to do an average of several places to find what I would consider good enough. The dining table and the kitchen counter are two places that matter if they are not level. Remember the sensor is in the front of the coach, so sometimes the rear, middle and front don't always agree.
When operating the Level up manually, the amount out of level will display as well - most of the time this is about right.
2012 GMC 3500 Duramax Crew Cab, SuperGlide 20k
2014 Cedar Creek 36B4, LP Onan, Level-Up, Trail-Air pin, electric fridge