Historically, those switches have been very sensitive to current surge. There’s some kind of buffering issue where when there’s a surge on the line the radios freeze up and then again, historically, the only solution has been to cut the current at the circuit box and restore in order to get them working again. And it does seem to get worse as the switches age. You can find lots of discussion of this in the forums.
So as far as the logic of it… If all devices of this model have that same vulnerability, and they’re all about the same age, then anything causing current jumps might cause multiple ones to fail. Even replacing a switch might cause a current jump that then causes another switch to freeze up.
You’ll find discussion of this on many home automation forums, it’s not a smartthings issue. It’s a Jasco switch issue with those older models. It does seem to be better with the newer ones.
So… You’re not the first person to report several of them failing either all at once or within a few days of each other. The first thing to do is check the wiring and all the connections and make sure everything is clean and tight. And preferably map the connections to make sure you’re not having current surges.
If the wiring and connections look good but you still have some non-responsive switches, try the trick of throwing the circuit breaker and see if that resets it.
( by the way, again going by historical reports, just using the air gap switch is sometimes not enough. You may have to throw the circuit breaker.)
Here’s a very old thread from six years ago on this issue: