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
این گفتگو قفل شده است و در نتیجه دیگر نمیتوانید در آن شرکت کنید.
What file format are you using? I had this problem with .flv files and sorted it out by converting them to .mp4.