Permissions in shared folder change after saving a Word document

Hello,

I have two user accounts: my main and private account (admin) and a work account. I created a shared folder on my macbook pro and shared it with the work account (read + write).

When I put Word (or any other) documents into the shared folder, I can open and edit them. But then, when I save the edited file on one account, my permissions (read + write) for the other account disappear.

For example: I set both accounts permissions to "read+write" for one specific Word file. I then edit the document in "work" and save the changes. When I get info, it's only showing three permissions: work, staff, everyone. My "main" permissions have disappeared. When I, then, switch back to the main account, I can't edit the file. I have to change permissions again.

Is it a normal issue? Is there a solution to this?

Greetings and thanks