Seeking is the action of placing the video's playhead at any position by clicking on the timeline. In most cases, this will work as you're familiar with on video applications such as QuickTime Player, Windows Media Player, and VLC. There are some rare cases when seeking might result in the video's playhead skips to the selected position for a moment, but returns to the beginning of the video. Here, we will provide some causes and solutions for this issue.
Cause: Not enough keyframes on the video file - Keyframes help the player understand how a video should look and sound at various positions. If there are too few keyframes, then the video can potentially have visual, audio, and seeking issues. In terms of seeking, the player may not understand where in the video you clicked because there isn't a keyframe close by. This can be extrapolated in longform videos (60+ minutes).
Solution: Add more keyframes to your video when you export it from your editing suite. Unedited videos from consumer/prosumer cameras or smartphones should already have enough keyframes.
Cause: A new video not yet fully cached on a CDN endpoint - A content delivery network (CDN) allows content (such as your videos) to be quickly accessible in all regions of the world with an Internet connection. When a video is uploaded to our service, then it is pushed out through the CDN. This is an extremely quick process. It can take some time for videos to be fully cached with the ability to seek in regions with slower Internet connections.
Solution 1: Allow the video to play through once in a specific region in order for it to be cached on that CDN endpoint.
Solution 2: Switch your video delivery option from Progressive to either Adaptive or Streaming in your Player Settings.