You might have a bend in the arm. If y
The back arm goes up against the trailer, extend the awning, and compare the arms. If it doesn’t, you might want to see how the arms look on another trailer. Mine did that once, and I just bent it back. All good now.
Mine does the same thing. Checked the arms, they are fine. Appears to be with the actual awning fabric. Rolls up straight until the last 6” then the fabric pulls it towards the rear and the arms don’t insert like they should. Haven’t had time to really look into it.
When it’s fully extended, does the fabric lay straight? If it’s not lined up evenly where it attaches to trailer and awning roll, it could cause this. If that’s the problem, you just need to slide it in the awning arm a little til it’s lined up