In the middle of one of our road gigs this past summer, the assign button for my combination patch busted, and dropped down inside. Fortunately, I was able (when I needed to) to turn the unit off and back on, and the kb defaults to combination mode so I was still able to scroll through the patches in combo mode to find what I needed, but it did delay me a bit while having to do this. It's in for repairs right as we speak.
btw...pressing harder will eventually give you grief. Contact cleaner worked for me. Made a big difference, but that's just my unit. Might not be feasible for you.
Just my thots...

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...L