Had this problem start happening out of the blue (as in NOT after rooting or accepting an update, etc.). First noticed it when playing internet videos (Facebook, embedded YouTube, etc.) on fullscreen, but then it started happening with all videos (whether using stock player, MX, etc.) for full movies that I have on my external SD card. Running stock rooted with TWRP recovery.
Wiping cache solved it completely for me. Of course, wiping cache with too new of a version of TWRP recovery caused my cache partition to be unmountable, resulting in boot loops and all kinds of issues, but that's another story entirely! Solved the new problem by switching to Philz recovery, wiped cache again, and everything was fine. I probably would've been fine just downgrading my version of TWRP as well, but I'm using Philz recovery on my Note 2 phone, too, so I'm fine with using it on the tablet as well.