We’ve seen this a few times now, and each time the cause has been a second machine on the network that was used for Ignition development. It goes like this: someone develops, and then performs a backup and restores in on another machine (usually moving from a dev server to production). The dev server is left running - but its demo expires. SQLTags history actually continues to log history, but with “Demo Expired” quality (something we should change, I think). Since the systems are both off the same backup, the have the same system name, so the data gets mixed.
The easiest way to track this down is to go to the database and see who’s connected. With MySQL, this is fairly easy from the MySQL Administrator, for SQL Server you can use the “spwho2” stored procedure, and for others… well, I’m sure it’s possible
Hope this helps,