We have a problem with our users losing access to some of the SOGo calendars they should be subscribed to.

We have a script that ensures all of our users are subscribed to certain important company calendars.
So basically, we first set the permissions for a given group (we do this just once, when a shared calendar is created).

sogo-tool manage-acl add calendaruser Calendar/XXX-XXXXXXXX-XX-12345678 '@somegroup' '["ObjectCreator", "PublicModifier", "ConfidentialModifier", "PrivateModifier"]'

and then we subscribe the group via a cron that is run daily, to ensure new users get added to where they belong:

sogo-tool manage-acl subscribe calendaruser Calendar/XXX-XXXXXXXX-XX-12345678 '@somegroup'

After this command is run, the status in the database is apparently correct, with someuser (a member of @somegroup) having FolderShowAlarms, FoldersOrder and SubscribedFolders. So far, so good and as expected.
However, as soon as someuser logs into the web interface and uses SOGo, they will drop the SubscribedFolders item, and thus will stop seeing the calendar.
Are we managing ACLs correctly, or is there a bug here in recent 5.12.X versions?