Anybody has idea how to prevent this from happening?

Can not find the reason directly. Please open https://gdh1995.cn/vimium-c/keyboard-test.html, turn off Vimium on it and reload page, and then press play/pause media keys to see what it will record.

Hello sorry it took so long, it recorded this when I pressed it twice:

It's because of the Code: KeyG: on every pause key, Vimium gets a g, and on the second the key sequence becomes gg, so it triggers scrollToTop.

You need to uncheck the option of "This forces the use of en-US QWERTY layout and can be helpful for non-Latin keyboards.", to let Vimium not use keyboardevent.code

I see, thanks it worked.

I got an idea to fix this mismatch when keeping "QWERTY layout" enabled, so could you do me a favor and test such zip files?

I have a customized version of Vimium, named Vimium C, and I've compiled its gdh1995/vimium-c@cc46d81 and got 2 zip files: vimium_c-1.86.2-firefox-cc46d81.zip, vimium_c-1.86.2-chrome-cc46d81.zip. You may installed such a zip on chrome://extensions and then test your pause/resume keys on its option page, and here's a tutorial: https://github.com/gdh1995/vimium-c/wiki/Test-a-zip-package .

Ok it works correctly for me with the Vimium C both in chrome and firefox