Storyline 360 - video replay's every time when we try to click on the seekbar in chrome

This one took me a long time to track down. I will try to keep the description short but let me know if you need more. It should be easy to replicate. We first noticed this when using Chrome following the Dec 4 patch. The platform is WordPress with LearnDash and the Grassblade xAPI Companion.

The problem manifests as mp4 videos embedded in Storyline restart at the beginning of the video when the user clicks anywhere on the seekbar/playbar if using the Chrome web browser.

After a lot of research we found that this is caused by the Grassblade Enable Content Security option. The fix is to disable that option (Grassblade / Settings / Content Settings / Enable Content Security). There are two reasons for this:

1) Function grassblade_security_check() returns the entire specified file without respect for the "Range" value passed in the HTTP request header, which is how video seeking works in HTML5.

2) This implementation uses an .htaccess file that is added to each xAPI module (Storyline project in this case) which rewrites the URL and causes Apache to apply caching rules and send HTTP response headers associated with .html files rather than the mime type of the requested file. Since default Apache applies "Cache-Control: max-age=0, private, no-store, no-cache, must-revalidate" to a collection of file types typically not cached (including .html) those headers are sent back for all file types including mp4. Edge and Firefox apparently ignore this and use the local cache anyway, and it seems Chrome did too until a recent update (perhaps the Dec 4 patch). If the client ignores the no-cache directive, then seeking happens locally without making a request of the server, which protects playback from being broken by item #1 above.

The bottom line is that in our case the issue is with Grassblade to fix and is not a Storyline bug. Others having this problem are likely affected by the same or similar cause.