Oh, the RV Trim Insert Moulding. I don't think that's usually a problem. In fact, I had to remove and replace some once and it was such a tight fit it was difficult to put on.
I'd think you could use some dabs of silicone underneath it. As long as it's not so much that you couldn't remove the trim piece if needed.
If your Trim Moulding is weak and or floppy you can replace it with thicker. Just be aware that the thicker you use the more difficult it is to fit in the track.
You can get new trim moulding at lots of places. Just be sure to get the correct width and the correct shape that corresponds to what you have now.
Here's one at eTrailer... but I have no idea if it's the correct size for your trailer:
https://www.etrailer.com/RV-Trim/Camco/CAM25113.html?