I am pretty sure the right side of my tailgate is not latching when I close it. How can I be sure and is there any fix for this?

 

Grease the latching mechanism as well as the little peg that it latches onto on that side, and if it's loose try tightening it up. The peg for mine is a little loose on one side, but it still latches so I haven't worried about it.

An easy way to tell would be to just grab hold of that side and pull/wiggle and see if the tailgate moves independently of the locking peg on the bed. The gap should be wide enough to see down in there.

 

I had the same problem about a year ago. I ended up taking the handle off and found the two rods in the door were all covered in road dust, etc. Cleaned them up and it latches like new.