The ailerons on a 152 should both be the same (1/2 or 1 degree of droop IIRC from the flaps) - there is NO allowance (unless the book has been rewritten very recently) for off-setting them in the Maintenance Manual for a heavy wing situation. On the 152 this is cured by reducing the angle of attack on the light wing by turning the rear spar attachment bolt eccentric bush.
152s will fly wing heavy with only one person on board (who is sitting on one side, not in the middle!).
On the Pipers you are allowed to cure a heavy wing situation by dropping a flap.
Some times the small door frame stiffeners crack which beef up the rear edge of the fuselage door frame which allows the frame to flex more than it ought to.
Because of the rotating latch mechanism, you have to make sure the door is properly closed (not wishing to teach you to suck eggs here). From the outside that's easy - a firm push on the door adjacent to the lock does it. From inside it is often difficult to get enough pull on the door closing strap to shut the door properly, best way then is to open the window and pull on the window frame towards the back of the door.
Another possibility is a door seal out of place that is preventing the door closing completely - either at the front or rear edge.
Interesting that on a 172 you can't open the door from the outside once it's locked for flight from the inside - not good if the RFFS people are trying to get people out in a hurry....