This isn't a bug, it's intentional. YouTube will skip back some amount of time on purpose if it thinks you haven't been to the video in a while. Even if all you did was click away from the tab for some hours.
Skipping back twenty minutes in time is not a feature. The reason it was skipping in the first place was because it would use a stale param on videos opened from youtube history.
Skipping back twenty minutes in time is not a feature. The reason it was skipping in the first place was because it would use a stale param on videos opened from youtube history.