I started having this issue on 12/31/18 where my rank would default to a three star and be zeroed out as well as all my stats.
I believe this started after viewing the replay mode? But after just sitting on the menu for at least 30 sec, my rank is reinstated.
But, unfortunately all my stats still appear to be zeroed out.
The only fix I tried on my own was to just close out the application and reopen it from steam. It appears to not have any affect on reversing the 3-star rank or any stats. The only "fix" is just waiting on the menu until my rank is reinstated, but even then, my stats still remain zero. I am trying to avoid reinstalling, so I came here looking for an alternative answer if that doesn't end up working. Thanks.