Issue title: During 200 % playback, using arrow keys skip to the end or starts over, both ways.
 Issue body: When I use the arrow keys to move back and forth for a few seconds, to hit my mark, it either constantly just goes to the end of the video, or pauses itself and starts over. I have tested whether it is a really impractical extra shortcut where if you press them twice, it does something, but it just seems to be a bug.

https://u.pcloud.link/publink/show?code=XZ2QBLXZHJvl0sRlLwuNYNUmp5GXFbvv6Sk0
 Comments: 
 Comment 0: Does it work as expected at 100% speed? 110%? Do you just use normal arrow keys? or shift+arrow,ctrl+arrow etc? I cannot see any keyframes in your video. sometimes seeking will struggle when there are not many keyframes
 Comment 1: closing due to inactivity
{'source': 'GithubIssues', 'repo_name_with_owner': 'mifi/lossless-cut', 'issue_id': 754546354, 'repo_stars': 12748.0}