I just went to my stockpile (phones removed from downsizing a couple of years ago) to replace a problem phone, and it took 4 tries to get one without hookswitch issues even though they were all working OK when put into storage (I had already weeded out the bad ones before storing, and two were ones that I had done a thorough cosmetic cleaning to have them ready to re-assign).
I believe the actual switch inside the phone has a rubber button with conductive ink - is it drying out in storage without being flexed on a regular basis?
