5th occurrence - steps on watch update, they match on the watch and the app, then the app runs a full sync and steps are deleted back down to the number of steps I had prevt

This is the 5th time this has occurred. I've had it happen on two different watches (Lily Classic 2 and Vívoactive 3) and I've contacted Garmin three times of those 5 occurrences. 

I see the steps on my watch, I see the app add the steps, the watch and the app match. All good so far. Then the app does a full sync and the steps go down, back to what they were before I added the additional steps. 

This is not a time zone issue - it happens any time of day (not just rolling over past midnight) and I've checked that setting on both watches and the app hundreds of times. 

Sometimes it happens early in the day, so the step count it goes back down to is like 900. Sometimes it happens later in the day, or after a run or a hike, so the step count it goes back down to is much higher. That doesn't seem to make a difference. 

That doesn't seem to be a rhyme or reason as to when it happens. I have yet to get a fix for this, other than they will adjust my step count as a courtesy for me this one time. The only steps I can take is to disconnect my device from the app, delete the Bluetooth connection, and basically reconnect everything like it's a brand new watch. Which is fine, I guess, but it doesn't actually tell me what's going on to cause the steps to be deleted. It's obviously connected, because it is updating the app, it just then goes and deletes steps after it syncs. 

Has anyone else had this experience, or have an idea what is happening in the app that is causing steps to be deleted?