Watch still syncs despite “Sync Failed - Device Connection Error” status

Getting some really weird sync behavior with the Garmin Connect 4.25.2 app on iOS 13.3. Watch is now on firmware 4.00:

- on the “My day” view I can see when the watch syncs and there’s always a green dot.

- After an apparently successful sync, if I tap on the watch icon to open the watch view, I get the red dot with the exclamation mark instead of the sync icon.

- If I tap the red icon with the exclamation mark, I get an error “Sync Failed - Device Connection Error”

What makes this a weird situation is:

1) This seems to have started happening after I installed the “Other” app, still on firmware 3.90. The behavior I describe in the next 2 steps seems to confirm this

2) Syncing never manages to place the “Other” app in the right order or in the favorite apps list

3) If I try to change the position of the “Other” app in the list of apps, it will never respect my choices nor will “favorite” position be respected (e.g. I have a “remove from favorites” option, but the app is not in the favorites list

4) All other changes and activities seem to be correctly synced

5) Moving from firmware 3.90 to 4.00 didn’t help

6) Following the sync troubleshooting steps from Garmin didn’t help: https://support.garmin.com/en-GB/?faq=9BcXLSQ4A22gasLarkUvH6

7) Resetting the watch data and settings (factory reset) doesn’t help

8) Removing and reinstalling the Garmin connect app doesn’t help

This is driving me nuts! I don’t care about the “Other” app anymore and don’t want to bother with troubleshooting that.

Anyone has a clue on how to get rid of the sync error?