Sentry Discourse forum notification mails have invalid DKIM signature

This Sentry Discourse forum sends notifications mails which carry a DKIM signature:

DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple;;
	s=sjc2; t=1524252263;

However, this DKIM signature is invalid:

Authentication-Results: <<spam control gateway server>>;
	dkim=fail reason="signature verification failed" (2048-bit key) header.b=jMb9G1Oi;

It would be great if this could be fixed, so that spam filter software would not mark the Sentry Discourse forum notification mails as forged and thus spam.

Other Discourse forums send mails which pass the DKIM signature verification, so there must be something odd about the Sentry Discourse forum setup.