If it turns out you need to use glue to repair broken plastic clips/retainers, you can try a product called Mr. Sticky. It's a two-part glue that works even in underwater applications. Quite an impressive product. There's also another one I picked up at a hobby shop that is a waterproof two-part glue.
If I recall correctly, it was a Devcon brand. When I tested these, they worked well. I repaired my driver's door panel assembly with this stuff and some tapping/threading of plastic behind broken heat rivets. Screwing in some machine screws with washers was part of it as well.

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel