No, the error is because Nginx has OCSP active (ssl_stapling), your certificates have the OCSP extension, so Nginx tries to get the OCSP response using the dns servers used in resolver directive and for some reason thoses resolvers couldn’t resolve the r11.o.letsencrypt.org domain (OCSP domain used in your certificates).
So, in your case, if you don’t want to see those errors, you can turn off ssl_stapling for your domains. You don’t need to add the directive in global nginx.conf because it will be overrided by your web domains conf.