I have one other suggestion that I don't think was mentioned. And it's not in ArchiCAD at all.
If it's only an issue in Teamwork, go into the BIM Server Manager, and check the Permissions of the Roles that each of your Users are assigned. There is an option to lock out access to Grid Elements by specific Users/Roles. If those Users don't have it checked, they will not be able to edit those elements under any circumstance.
Unfortunately, ArchiCAD does not give you a reason when you cannot edit something. It just stares at you blankly. It would be nice if it said, "you can't do that because..."
I hope this helps.
Chuck Kottka
Orcutt Winslow
Phoenix, Arizona, USA
ArchiCAD 25 (since 4.5)
Macbook Pro 15" Touchbar OSX 10.15 Core i7 2.9GHz/16GB RAM/Radeon Pro560 4GB