I have a problem with my HTC Desire 816G (MT6592). Whenever I install the Android M ROM, internal storage doesn't mount. My phone's internal storage doesn't appear in USB mode and nor in file manager. The phone's features like Gallery, Camera, Recording, etc., are not working on all Marshmallow ROMs. Lollipop and Kit Kat work fine. I didn't have this problem with Marshmallow ROMs before. I've been stuck for around 2 weeks now.