coach tilting

i have an 06 monaco knight DP equipped with 8 air bags. when i store it i dump all the air out of the system (gauge reads 0-0) the coach lowers a bit and is level. one day later the coach has a 2 to 3 inch lean to the right. and a bit lower to the front (half a bubble) when one dumps the air you would not think the air bags remain inflated, hence why dump the air at all? or does air remain in the bags and there is a leak on the right side? confused.