Can't assign permissions to multiple roles for a domain

In a new project based on archetype (12.0.0):

• Go to CMS
• Go to Admin > Control Panel > Permissions
• Select any of the domains, e.g. autoexport
• Grant one group permissions as one role, and grant another group permissions as a different role, e.g. author as author, editor as editor
• When trying to add the second group, the group does not get added (no error shown in the CMS UI) and an error is triggered in the logs (see attached stacktrace)

What happens in the background is that any permissions are added with the nodename hipposys:authrole. Since same-name siblings are no longer supported, adding the second group fails because a node with the name hipposys:authrole already exists. Using the role as the nodename should fix this (that's how the nodes of the default archetype permissions are named).

This issue also occurs on the latest snapshot version.