If the system preference SearchEngine is set to Elasticsearch, attempting to use matching rules fails with the error:
Can't locate object method "fields" via package "MARC::Record=HASH(0x9ce46a8)" (perhaps you forgot to load "MARC::Record=HASH(0x9ce46a8)"?) at /home/vagrant/kohaclone/C4/Biblio.pm line 2713.
It appears that the contents of the variable assumed to be a MARC::Record object are literally a string and not eh object. I was able to narrow down the issue to something going on in C4::Matcher::get_matches.
*** This bug has been marked as a duplicate of bug 18131 ***