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When I'm playing Spotify, I have this exact same problem. Currently, I am running an Acer Chromebook R11, and I have found a solution for now. However, I am not sure this will work on other devices, so do not take my words for granted.
1. Close out Spotify if you are playing it
2. Shut down your Chromebook with the "Shut Down" button
3. Turn on your Chromebook again
4. Go to your Spotify and play a song, it should not pause at 9 seconds.
If this does not work on your Chromebook, then I am not sure. That is the only solution that I have seen to get rid of the problem.
P.S: If you shut it down again, Spotify will reset to pausing at 9 seconds. If you get worried about that, do the process again, for it has worked for me so far.
My Chromebook has a problem where Spotify pauses momentarily at 9 seconds when on the web browser. My school disabled apps, so I cannot download the Spotify app. You answered someone else and said this was an individual problem. This is not. People are posting about it everywhere, places like Reddit. Please fix this problem.
They still haven't fixed this? Former Spotify subscriber who tries this every couple months -- and Chrome OS versions -- hoping there's been a fixed.
Same issue as everyone else. Pauses on every track at 9 seconds. Resumes after a second. Very annoying interruption to music. Clearing cookes and cache doesn't help, neither does rebooting Chrome or resetting network.