is it possible for the trailer axles to get out of alignment?

Yes but it isn't that obvious when backing because of the low speed and short distance. It would be obvious at highway speed. If the axle was out of alignment enough to effect it backing up,it would be pretty obvious by looking at it that it is messed up.

 

Yes they get knocked out from bouncing off of curbs (and other things) all the time, you can see it in mirror by comparing the distance between the fog line and the tires on trailer to the distance between the truck tires and the fog line when driving straight.

 

I found some trailers off track if the pins are not fully engaged into the holes on the trailer that the tandems slide under when you want them transfer weight.

 

Lol No , but you can find one in the lumber section next to the board stretchers.
Seriously though , the fogline is the solid white line on the shoulder.

 

No