It is just a hunch, but I suspect Tableau Server cached something and refuses to get up-to-date, showing the old erroneous view.
The easiest way to check is to reboot Tableau Server machine, or even restarting the server app via its monitor utility or tabcmd may do the trick. If that is not desirable, then try re-publishing this workbook with different name in a different project, etc. to trick Tableau into not using cache. If that works - reboot is needed.