Lucky you. Restart didn't fix my back button issue. It's just the back button setting. Other functions on that button work fine.
The fix for the back button (believe it or not) is to turn on water mode, then turn off water mode. It works, but I have no idea why.
As to the google wallet issue, I have that issue as well. It appears to be when the Google Wallet App updates. I am thinking that since they switched from Pay (which was a built in software on one of the updates) to Wallet, which isn't one of the "native" apps, then when it updates, it is removing and reinstalling the app which is killing the setup on the watch. I have noticed on my phone, some shortcuts I have on my home screen disappear when those apps update also. Not a stretch to think that could happen with Wallet on the watch as well.
I think the issue is for the Google Wallet team to fix vs Samsung. I doubt Google cares anymore about fixing something on the Samsung eco system any more than Samsung cares about fixing their watch for us to use a Google app since they removed all the useful functions of Samsung pay.
I have to thank them for removing absolutely every reason I had to stay loyal to the brand. For the first time in a very long time, I have no reason to only consider Samsung in order to keep my ecosystem working. All of the exclusive features I depended on are now gone.