This occasionally happens, not always. I currently must avoid touching the playing [https://www.deezer.com/en/ Deezer] tab when browsing. I've also encountered playback starting for a stopped track in the same situation and an album starting to play from the beginning right after the last track ends. I feel that this may be related to the newly changed Firefox `autoplay` preferences (about:config). As I recall the issues appeared in Firefox 62.