AVPlayer miss visual part of video but sounds play well

Hi guys. Can you help me please?
I use AVPlayer in my xamarin.ios proj for playing video file. In previous version of app the is video without any sound and all was right.
But now customer ask to add new video with sound and I don't see any video, hear sound and see quicktime logo on screen.
Video in mp4 format in both cases.
Problem handled only on iOS 10, on iOS 11 all right.
Thanks.