Imported video starts with white frames, please help!

How to get rid of a white frame/s that appears at the begining of embeded video after Export Video/Media.

• Embeded video starts with the white frame as if it has contained one in the file... but there is no white frame inside the imported video file for sure. The imported video contains only frames showcasing the scene,
• Moreover whole project that contains this video starts form the very begining without any skips or lags. Vector animations start seamlesly from the begining of the timeline but not the video,
• To make it clear, the the problematic embeded video should start sharp from the very beginning of the project-animation,
• In relation to that, what I need is to get know, how to solve it without any animation tricks like masking, moving, alpha modifications,
• I'd be greatful receiving help, explaination what may cause this issue and how to solve it,

cheers!