When the side case on my BMW R1200RT wouldn't open recently, I knew it was time to take it apart and inspect the lock and internal mechanisms for problems. Fortunately I was able to get the pannier open, and expose the screws inside for disassembly. After cleaning, greasing and making a linkage adjustment, the case handle snaps open nicely now. This example is from a 2012 model year, other model years may vary.

►To purchase:
https://amzn.to/3wiL9tq (Super Lube 21030 grease)

As an Amazon associate I earn from qualifying purchases.