I whacked off the Sepolicy for mediaserver and mfc_device coz I thought the external/sepolicy has included them but I was wrong so (just my guess) that's why media apps get FC tho but not so sure. Anw, I restored those sepolicy locally and built a build with those file for newest Slimsaber tho. @OP: you can test and tell me if it still exist or not. Not so hopefully about the vid playback from Gallery apps but I hope youtube and camera would act normally again.
If you find me deserve with all of my work, you can either press "thanks" or donate to help me with my finance for university next year. Thanks!