The mistake you are making is to pause then copy. You may or more likely may not get a clear image. Most frames are blurred but when run quickly we don't notice. First download a player like VLC and from the top bar click on View then tick the Advanced Controls from the menu. The bottom left of your VLC screen will then show 4 extra controls.
View attachment 314802
The red dot is record then snapshot, loop and advance frame by frame (for approx 25 frames). You can choose from the frames which you want to keep. You can click on the snapshot.
Also in VLC you can adjust brightness, colour, hue and other settings to improve the quality of the film. VLC can do lots of other things as well as saving snapshots and video clips it can convert videos and even record from Youtube.