Useful Information

The lock that appears is configured to run after our online servers have not received a request in 30 minutes.
A request happens when you do something like add a transaction, open an account statement, run a report or change tabs.

You could technically be working in SCO (within one particular screen) without sending any requests.
Once you make a request, the lock will appear, so it can appear like that lock is occurring while you are still working.

The 30 minute timing meets current data protection best practice advice.