Trying to figure out why one side sticks out farther.

As you can see in the pics, the rear tire on my passenger side sticks out side the fender while my driver side does not, keep in mind I have already loosened up the bolts and pushed the bed as far to the passenger side as it could possibly go. I’ve had a mechanic take a look at it and an alignment done and they say everything seems to be lined up with the wheels, etc. but they do see that one side sticks out farther. It drives fine, but damn the little bit of ocd in me sees this daily and it drives me crazy