The plastic strip that fits into the metal strip to cover the screws is purely decorative (and some water repellency). I'm guessing your original hardware is rusted, and dimensionally challenged. You can replace them and/or shoot new screws in to hold the metal strip. Pull the plastic strip out, shoot screws (self tappers) straight through the metal plate, into the RV wall. Seal the penetrations with silicon, put the plastic strip back in. Liberal use of silicon sealant does not hurt anything. Clear as mud?