I may need to qualify this: having disabled URL lookups I'd had no problems at all, but this morning I had a repeat of the above symptoms (CPU load to 100%, everything stops responding) and there had been no lookup of any kind... and no errors in the debugging output. Hmmmm

Maybe I'll have to download the sourcecode from git and play, but I wrote software for research purposes, not really "professionally" so not sure I back myself to find a fix

@jonas No sadly not, I tried that and it did the same after AudD failed.
It doesn't happen instantly - in the debugging output it fails to get something from a URL, so falls back to a different provider and succeeds -- and often continues playing into the next song, but soon the CPU usage goes up and then everything stops responding.

On my Macbook Pro, running MacOs Catalina, Strawberry sometimes starts using up 100% of my CPU and becomes unresponsive (the active track plays, but no controls work. When the track finishes, nothing happens).

Running Strawberry from the command line so I can see the debugging output, there is a common theme: the crash always seems to occur shortly after a failed URL transfer, e.g. a failed lyric look up. I tried disabling all lyric providers and everything worked until it ran a track for which there is no cover art. Again there was an error inthe output (here: 08:10:51.792 ERROR MusixmatchCoverProvider:227 Musixmatch: "Error transferring https://www.musixmatch.com/album/unknown/settlers3 - server replied: Not Found (203)") and shortly after the CPU usage went up to 100% and Strawberry stopped responding.

I guess there is a workaround for now, which is that I disable all lyric and cover lookups, but this appears to be a bug to me