Have you tried it by NOT using Moodle Mobile? I have my Moodle set to use only one theme and have tested with multiple types of devices, and depending of the video format, the video just about always shows up just fine.
I've tested all the MS Surface Pro's, a few Samsung Android tablets, an iPad, and various Android smart phones, usually with no problems. The only time I have had problems was when the video was in a format not supported by a device. I had really good success with .mp4 videos.
Out of curiosity, since I just started maintaining Hot Question, I just put a video (.mp4) in the description of a Hot Question, logged in with a student account on my Samsung S4 phone, watched the video, typed in some text, and it all worked fine.
The main reason I skip using Moodle Mobile is due to my own poor eyesight. I like being able to zoom in and on my phone it just seems to work great whereas the time or two I tried with Moodle Mobile it wouldn't.
I also recommend installing the Generico filter as you can set up some nice video display options using it.