When a user X shares their entire home folder with another user (2 users: Y and Z), users Y and Z cannot share any subfolders with other users (V or W). They can only share via email or link to 3rd parties.
Unsure if this is a bug or by design. It seems strange you can share someones subfolders to 3rd parties but not to other internal users.
I checked all the permissions, they have all been given.
Customer support service by UserEcho