Multi-domain dispatcher setup isn't working | AEM 6.x, Dispatcher

Multi-domain dispatcher setup using Resource Resolver mappings is breaking AEM features on the publish instance such as the User Administration UI.

Environment

AEM 6.x

Cause

When Resource Resolver mappings are used to map URLs then this can lead to URL mapping conflicts.

For example:
You intend to map /home.html to /content/site/en/home.html using this resource resolver mapping:
/content/site/en/home:/home

That works, but it also has the side effect of mapping requests for /home/users to /content/site/en/home/users.  That breaks AEM's User Admin UI.

Resolution

Use a multi-domain mapping solution that is domain specific leveraging /etc/map instead of resource resolver mappings.

For example, this solution [1].

[1] https://www.cognifide.com/our-blogs/cq/multidomain-cq-mappings-and-apache-configuration