WARNING! Don't install beta 14.12 - after update no settings change is possible in GC.

I confirm this. The issue is worse than before 14.12. Now, not only the data screens are impacted, but the whole settings section 

Confirmed. Oh, dear...

Happened to me, someone mentioned you can re-install GC on your phone or remove the phone from the device list and re-add it. I did the latter which solved it for me, but I had to reconfigure Garmin Pay, perhaps if you re-install GC you won't have to.

Another one bug on 14.12 - see here

i'm lost there

There are workaround to the problem.

You must change your default language on phone to english (my def setting - german) Than this is important! on the watch (your sync not work - haha) go to settings ->System and change language to same language as on phone. Congratulation! Now you can see and edit your fr255 settings :)

and change your language back to your preferred language.

My solution was to forget device from BT setting and then re-pair it  and it did it fine no loss of Garmin Pay. I also deleted and reinstalled the GC app as a matter of course.

this does not work, both my phone and watch are set to English still broken 

The point is not have english as default, but change language to some other on both watch&phone, make a sync and go back.

I can confirm this is a workaround 
Garmin-Kevin This is interesting and will help solving the issue. It looks like this may be an Internationalization issue, for non-english languages.