I don't know how it's supposed to work on a phone, but I've encountered that problem on my laptop before. I've tried adding a video, and it'll end up getting turned into a link instead. Since that's not where I wanted it, I go back and delete it. I don't know if it's a compatibility issue or some kind of glitch, but if I remember what is was that I wanted to add, I might try again on a different day.
Lately I haven't had any problems with adding videos, but I have had some with uploading images. I'll do the same with them - try again on another day.
I've never tried adding content via a mobile, but the only time a video has become a link instead with me is when I accidentally gave the wrong URL. Fanpop didn't recognise it as a video so it made it a link.