I reinstalled the whole system, the plugin (version 12/19), re-did API credentials, updated ytdl core and tadaaa: works. Sort of. I have the same button-issue as cmoulliard (doesn’t bug me too much) but now I get the 2/3 thing again (stops at 2/3 of the song)… There was a solution for that I guess somewhere in spring? I go researching. May take another 14 days…
Edit: ok, took me an hour to find out: the mpd needs a tweak, too. For anybody running in the same issue: can be found in Dec 2019: