it's just vinyl trim insert that slides into the aluminum trim.
It was likely put in a bit too tight and shrinkage causes it to pull out. I'd go all the way to the end of the strip, it is likely folded over under itself with a screw to pin it. Take that screw out to see if you have any slack.
otherwise, just replace the whole span of it. It's cheap....and it would give you a chance to inspect all the screws under it.... easy job.