5th wheel receiver hitch latch not completly closing

When I've had this problem (Reese hitch) it was because I didn't line the pin up well with the receiver head. The trailer pinbox should shift slightly to center itself, but I've learned that it sometimes doesn't and then the jaws won't completely close. It took a couple years of occasional issue before I figured this out. Best thing to do is release the handle, pull out a little, then backup and hit it again with a bit more gusto.