This bug exists in the Zabbix 6.4 series from version .13 to .18. Not sure about 7.0 and above.

Makes heavy use of the HostMetadata line in the zabbix agent--

Configuring that line using puppet, to dynamically add a host to various groups and templates.

For example, one of systems might have:

HostMetadata=:kernel=Linux:osfamily=Debian:org=CTSI:virtual=vmware:role=stage:server=yes:module=apache:module=shibboleth

 Autoregistration actions that add this host to "OS/Linux", "OS/Debian", the CTSI org, etc.  The 'module' means it should be added to "Application/Apache" and "Application/Shibboleth", and have the appropriate templates added as well.

Added the Shibboleth template  and updated the hostmetadata for the systems running shibboleth.

Then created a standard autoregistration action:

And it didn't work.  If added a trailing colon ( : ) to the hostmetadata line:

HostMetadata=:kernel=Linux:osfamily=Debian:org=CTSI:virtual=vmware:role=stage:server=yes:module=apache:module=shibboleth:

And it started working.

Is this a known bug?