Windows 10 sign-in will lock your machine if you have your mobile device paired with your desktop/laptop machine. This will keep the machine secure when you are away.
Unfortunately there is an intermittent bug in Windows that has been present since it was first offered long ago. When you log back on to Windows, it complains that it cannot find your mobile device.
This suggests a problem with the error handling which could be redesigned to wait 5 seconds and try again a few times in a cycle before it throws an error.
This exists with various model iPhones and Bluetooth radios. It also exists in various versions of iOS as well as Windows 10 updates.
This post simply is intended to call attention to the ongoing nuisance of the dynamic lock situation. Posting comments on forums does got some confirmation but no solutions are know.