I just wanted to update this thread with two more options though I haven’t tried either yet.
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Conductive Rubber Keypad Repair Kits - like used on this video: https://www.youtube.com/watch?v=6vq0S4UU9yM
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Deoxit F5 - which explicitly says is safe for carbon, plastic and membrane switches. I’m assuming its safe for rubber assuming thats what the membranes are made of, however I keep hearing otherwise (even though you are not putting it on the rubber it might travel there. Mineral spirits is supposedly bad for rubber so I don’t know why they list its safe for membrane switches).
I haven’t tried either personallly so correct me if I’m wrong.