I’m sure that’s very frustrating.
There was a recent bug in the Amazon/SmartThings integration, but I thought it only affected virtual devices. So that would affect your Alexa helper group, but not physical switches.
That particular problem was fixed this week, so if you do a Discover new devices, it should be OK again.
If you’re still having problems after that, I would get in touch with support@smartthings.com so they can look at it from their side.