Verify a Transaction group has been completed

I have a transaction group that saves 6 tags to a database, I have a Boolean tag that is the trigger to save the values. The transaction group resets the Boolean to false when it has completed.

The problem is that I have noticed that sometimes it takes the Boolean a few seconds to reset and sometimes it takes it a ~30 seconds.

How can I very when the transaction group has completed its transaction? I need to read some tags when its done and need a consistent way to do it? Thanks