First thing to check would be air pressure in the tires. A difference of 5psi could cause it depending on the tires. Next, check to make sure you don't have a bent blade. If neither of these are the problem and it is a new mower I would contact the dealer where the mower was purchased.

and.. on pavement.. measure both sides of the deck height ... ground to bottom of deck ...

that should be easily adjustable... if they are off ...

as an aside .... why do you cut the lawn so short????

ken

If it's not tire pressure, refer to your manual for instruction on how to level the deck. It helps to have a JD deck gauge- about $10 at JD. There is a forum here at GW for tractors where you can get very good answers for this and other more complicated issues you may run into.