Makita palm sander (BO4550) not gripping sandpaper

I have an old Makita palm sander that I hadn't used in a long time.
When I tried to use it, the sandpaper kept coming loose from the "clamper" almost immediately after turning it on.
Specifically, the clamper arm doesn't stay pinned down and instead pops up, opening the teeth and releasing the sandpaper.-- clearly, this makes the sander useless.
- Before I take it all apart or throw it out, any easy fixes for it?
- Does it sound like I need to replace the "clamper" (and/or "foot") or is there a simple repair?
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