I had to update to 2021 mid project. As a result I lost a custom subassembly. There needs to be a way to update the subassembly files in the C3D update. Also this is huge problem for BIM/C4C3D. If I use the custom assembly on one machine to build a corridor then another user (or me on another machine) tries to update the corridor the custom subassembly files cannot be found for other users (or other machines).