I will be watching this thread as I am having a similar issue. I was on my second Versa 2 as my first one got possessed when I'd had it about 6 months and got stuck in reboot loop where it would restart about every 7 seconds continuously until the battery died. (There was no way to even turn it off. It was completely unresponsive.) Even after I let it sit for a couple of weeks with a completely drained battery, it resumed the reboot cycle again as soon as I put it on the charger. Since it was under warranty I received a replacement, which worked for about a year. Then that one suddenly stopped counting steps and reading heart rate, so it could track absolutely nothing and become basically a watch that would notify me about texts and emails and let me check the weather. I dug out the original Versa 2 and put it on the charger just to see what would happen, and by some miracle it charged up normally and began to function again, so I've been using that one for the last 6 months or so. This past weekend, that tracker suddenly decided not to charge. Everything was working just fine, but that is irrelevant if you can't charge the battery. (BTW, the tracker gets very hot when placed on the charger now, so I'm not attempting to charge it again.) I kept using the tracker until the battery ran all the way down today. Then, I pulled out my second Versa 2 (in case you are having trouble keeping track, that would be the replacement tracker that I had received when the first one went bonkers). I charged it up to see if it was still not functioning as a tracker, and lo and behold, it was counting steps again and also floors. The heart rate monitor was still not working, but I figured that I could at least track steps and floors even if I would not get credit for the calorie burn or active minutes or get any type of sleep data.
Here's where my issue aligns with yours: Now, every time this tracker syncs, it wipes out all of the data from the previous sync. It took me a minute to figure out what was going on because I only noticed that something wasn't right when my steps-per-hour were showing not completed for the three hours that had passed since I started using the tracker and I knew that I had done them. I pulled up my dashboard, checked the bar graph showing my steps, then sync'd the tracker, refreshed the dashboard browser window, and watched all of the bars of steps previously logged by this tracker disappear and my step count total for the day drop. Every single time I sync the Versa 2, it wipes out all of the previously logged steps leaving only the steps that have been logged since the last sync. I did a factory reset on the tracker. I did a force stop and cleared the cache on the app. It is still happening.
I used a Charge 2 for 3 1/2 years until its battery was toast and I never had any of the funky issues that I've had with the Versa 2. I love the screen because it is so much easier to see than the Charge screen is, especially in sunlight, and it's more comfortable to wear, but the number of technical issues really is ridiculous.
