SpamAssassin does not detect HTTP(S) URL multiline mismatches

Issue

SpamAssassin does not always detect HTTP(S) URL multiline mismatches.

Corresponding lines added to /etc/mail/spamassassin/local.cf:

body HTTPS_HTTP_MISMATCH eval:check_https_http_mismatch('1','10')
describe HTTPS_HTTP_MISMATCH HTTPSMismatch
score HTTPS_HTTP_MISMATCH 2.0

Some of the messages containing HTTP_HTTP URL mismatch are detected, some not.