Why is the video not rewinding in the video tag?

Question

HTML

Good afternoon!
I use the video tag with src specified. The file itself comes from the server. The essence of the problem: if I try to drag the timeline slider, it does not change anything at all, the slider goes back even if I drag it to an already loaded part of the video.
What can be done about it?

Answer 1

Check video file. Download and run locally.
Perhaps because of the structure (not quite the right word) of the video.
This happens if the file contains only changes to the video image.
Direction of information search - video encoding.

What can be done about it?

Recode.