Is the issue that you make the change and it doesn't take? Or that you see the change but come back to it later and the change is lost?
The physical inventory list is refreshed every time the worksheet report is previewed or printed and the 'create workfile' option is selected. While you are entering qty changes, don't reprint the worksheet report.
I wouldn't necessarily suspect network rights or opportunistic locking issues, but ensure that these are set up correctly.
Could you indicate the keystrokes that you are using?
Perhaps add the 'Quantities entered' column to the grid so that it is easier to see whether the qty changed ("Yes") or if a change was not registered ("No"). In case entering a value is being cancelled instead of saved.
_________________________
Regards,
Softrak Tech Support