This artist Chimano Wikidata is linked to English Wikipedia but there is no summary/except from this Wikipedia page showing up on artist page, above summary.
Do you know why?
There are several ones not working, actually:
With no errors in the JavaScript console.
I tried several MBS languages and deactivating userscripts.
Just a delay usually, apparently as Wikipedia throttles requests. If I reload an artist page a couple of times the summary usually appears (all of those Wikipedia summaries are now appearing for me).
As riwood said. I forget where I read it(here or ChatBrainz) but wikipedia has been heavily throttling requests which is causing the issues with the summaries. I see them maybe 1 out of 10 loads(I did see it on your first linked artist when testing)
Thanks so much for your replies!
You’re right!
Maybe it’s because of my WD to WP userscript (which apparently never gets blocked). 
Seems like lately the script is getting heavily throttled as well.