After update on Huawei P20 to Android 10, watch started to disconnected if I open an App. Battery is drained connecting/disconnecting constantly. Updates on Samsung APP did not correct this yet.
I erased phone and watch but is the same situation.
Here what Samsung said and is working so far.
1. Go to Settings → Apps → Galaxy Wearable → Storage → Clear cache + Clear data
2. Go to Settings → Apps → Samsung Accessory Service → Storage → Clear cache + Clear data
3. Go to Settings → Apps → Gear S/Fit Plugin → Storage → Clear cache + Clear data.
Also, please try to turn the Gear device off and turn it back on; if this does not solve the issue, please perform a Factory Reset by going to Settings → About Gear / Gear info → Reset Gear.
You should also make sure that the Galaxy Wearable application and the Gear S/Fit plugin are not disabled by the Battery Optimization menu.