Do not shut down the computer containing the master model while other users are working on their working models. They will not be able to save their changes to the master model.
If this does happen, to avoid losing any changes, follow the steps below:
Keep the working model(s) open on the client computer(s).
Restart the computer containing the master model.
Open the master model on the computer containing it and autosave the model.
Click Save on the client computers to save the working models to the master model.