If there's an issue with video playback on the Mini it almost always has to do with video file compatibility.
Supported Video Formats:
XOGO supports MP4 and MOV videos encoded with the H.264 codec. Do you know what file type you're currently using?
Resolution Requirements:
The Mini supports a maximum resolution of 1920 x 1080 pixels (1080HD). If you load 4k videos into it, you'll see stuttering or they may even cause the player to crash and reboot. What is the resolution of the videos that you are using? If you're not sure, feel free to send us a sample and we'll take a look at it.
Video Conversion Tool:
If your videos need to be resized, for example from 4k down to 1080, there's a free tool called Handbrake that works great: http://handbrake.fr