Missy, something is blocking your shell from opening. I know my rear shell seems to bind ever so slightly just at the end. I've not figured out why, but I know something is binding in mine as well.
Here's a picture of the pocket stop, looking from underneath the trailer. This is where the lift arm goes into the upper shell:
https://www.trailmanorowners.com/for...pictureid=1908
Take pictures the the pocket 4 pocket stops for the shell that does not open fully and post them here. Maybe we will be able to see something. Also, is it possible some one tinkered around with the pocket stop bolt for one of the lift arms? They are exposed when the trailer is closed.