Check your gas tank. I have a Craftsman with the B&S engine with the same problem. The new gas tanks have coating on them that peels off. Look inside the gas tank...
I have a Craftsman Silver 5.5 walk behind mower. It has the 2 height adjusters on the same side.
One side is off by 1/4". The front & back right is 3.25" and the front & back left is 3".
Can this be adjusted? Could both Axle assembly be twisted?