Ns8-mail: Public Mailboxes group assignment not working

ns8-mail v1.3.4 / v1.3.5-dev.1

When configuring a “Public Mailbox” (or “shared”) for the first time, it is allowed to add groups and assign ACLs to them. Although does not seem to be working (no shared mailbox seen on user’s account from a mail client). If assigning plain users then it works.

Editing the public mailbox afterwards shows a warning about member not found referring to the group.