[Bug]: User does not gain file/folder access when joining a remote share group

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

See #51000

Steps to reproduce

1. Server A shares a file with a group X in server B
2. User P is added to the group X after the share

User P does not have access to the file. Any user(s) part of group X before the share do have access to the file.

Expected behavior

User P does have access to the file.

Nextcloud Server version

master

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start by reading issue #51000, which this report references, then trace the remote share flow for a user added to a group after the share exists. Reproduce the two-server scenario described here and verify that the newly added user gains access while existing group members retain access.