It doesn't look like there is a period timeout, so that is good ... however it appears as though the media player usage doesn't reset the timer when it is playing (I know this is how it works when I listen to music)

Perhaps you might try a different media application and configure it to have the application permission:

Interaction > Security Timer Reset

to a value you of Allow. This will allow the application to reset the idle timer so that the device doesn't lock when it hits the inactivity timeout.

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