What file format are you using? I had this problem with .flv files and sorted it out by converting them to .mp4.
Lesson
Video player appears duplicated on answer screen
Энэ мэтгэлцээн түгжигдсэн тул та цаашид хариулт өгөх боломжгүй
What file format are you using? I had this problem with .flv files and sorted it out by converting them to .mp4.