Sharing folders will sent email share accept invites, which are causing issues

As stated in your own README:

Guest users automatically accept all files and folders that are shared with them. This is in constract to regular full users (who have to actively accept incoming shares since Nextcloud 18).

Issue: Nextcloud is still sending e-mail accept invites after sharing another folder with a guest account. When that user tries to click on that accept invite email link (/apps/files_sharing/accept/ocinternal:29 path), the user will get an error message: "Access to this resource is forbidden for guests".

The user actually does have access, if the user just login and look at their folders on the root level. That being said, it's very confusing for the guest users who are getting this email.

Expected behavior: No unnecessary and invalid email invites when sharing additional files or folders.

Solution: Since sharing folders are accepted by default, avoid sending an invite email for sharing additional folders. Try to validate if the user is already active (eg. has a password been set) and do not send any more mail invites.

Thanks!

Start by tracing guest folder-sharing and email-invitation handling, including the /apps/files_sharing/accept/ocinternal:29 path described in the report. Verify how an already-active guest is identified and test that additional folder shares do not send invalid invitations while initial invitations still work.