I found out that Spotify on my Oneplus 3 doesn't pause anymore when I press the microphone button on Gboard to activate voice typing. When I hit the mic button, the music just keeps on playing.

I used that in the past so I know that this was working before. In the past when I hit the button, the music would pause and when voice typing ended, it automatically resumed playing.

I deinstalled all gboard updates and used the version that comes with my phone to make sure the cause is not an update of Gboard. Issue still persists, so Gboard is ruled out.

Since I don't use voice typing every day I cannot tell with which Spotify version the issue started.