Sharing calendars with group not working

Nextcloud version: 18.0.1
Operating system and version: DSM 6.2 (Synology NAS)
Apache or nginx version: Apache 2.4
PHP version: 7.3

I have a few users and a single group, plus an admin. I can share files (as admin, and as group admin) with the group, but I cannot share a calendar. Calendar share works for individuals, but not the group.

The group has a space in the name (eg “Word1 Word2”).

If I create a group with no space (eg “Word1Word2”) the sharing works.