That is indeed strange. Usually when things happen around a certain time regularly, it’s due to some maintenance procedure going on at that time- database backup, virus scan, etc.
Are there any operations scheduled for that time?
On the FactorySQL front, are there any messages from around that time in the Error log (Help>Log Viewer)? When you go to the groups, are the values being updated in the frontend? Is the “execution count” incrementing?
Also, which OPC server are you using?
Regards,