Tablet shuts off after a while (when having Mediaplayer opened)

[Elowan]

hi there,

yesterday, my Nexus 7 flo powered off completly two times.

I was watching some video with the on board player then locked my tablet and put it away for some (longer) time - maybe 1-2 hrs. Then I picked it up again and I had to turn it on - because it was off.

I left the mediaplayer running (video was paused) before I locked it by tapping the powerbutton 1x

First, I thought this may drained the battery, but it wasn´t the case. Power was still at around 80%.
I startet videoplayer again, paused it and locked screen. This time, I left the device connected to powercord the whole night.

this morning, the device was "off" again. looks like it has shutdown it self again...

After watching video again today, I left it locked again for like 30min and it has not shut down itself.

Hmmm, maybe I should just wait longer, until this shutdown happens?
Yesterday, it was conencted to WLAN all the time, but actually, it has no WLAN avail... besides this, I can not imagine any other significant difference, to yesterday...

I did not noticed such behavior in the past few days (but I did not have mediaplayer opened, when locking tablet back then - so I think this could be the issue)

Is this a know issue / bug / feature?
Is there may a logfile, that will give some clues, why it has shut down?

Cheers!