The method of molding attachment was with plastic clips only on the early 850s (pre-95), and was changed to double-sided adhesive tape in adition to clips on 95 and later cars. On the 95- cars, the adhesive tape does not run the entire length of the molding. Instead, there is a thin vertical piece at each end of the molding. Presumably, this was added to address the very problem you experienced. From the diagram, the length of the tape strip is about 2mm less than the width of the trim. It is positioned at each end of the molding so that the edge of the tape is 2mm inside of the edge of the molding.

The factory manual I have says:

"Double-sided adhesive tape (P/N 9511020-1) should be used as a service solution on cars where there is a gap in the front edge of the door trim molding".

Leon