Cannot sync with Garmin Connect

I have to reboot this vivomove style watch every time it cannot sync with garmin connect. Then it happens again after 2 to 3 hours. 

The heart rate status and notification is reflected (bluetooth is connected), but the activity, sleep, etc are not synced when this happens. 

Running v.4.00 (ASIA)

Definitely not smartphone issue. Occurs on Samsung galaxy S10, S20, and iPhone 11. 

Any advice will be appreciated.