Have you tried it with the IOS version also? Would be quite interesting to know whether this is a platform or a general problem in your case.
At least since my upgrade to 4.15.1 I have not seen any sync issues yet.
I cant sync my 935 data to garmin connect mobile andriod after update too. I am using samsung s9. Is it the problem of ny phone or the app??? I dont want to reset my watch as i so much want to keep my workout data. Also i am not sure if resetting my watch would help. If anyone andriod user succeed in syncing again, would u please share the trick? Thanks a lot!