Moved this to our Server section in the hopes that someone has a bit more info.
If you open the workbook locally in the Tableau Desktop for editing /for any changes
then there will two possibilities on the data source level...1.Either it can uses the Local extract files as data source..2. if you have published the Extract file to the tableau server already then it will be placed in the Tableau fast data engine and you can connect that server as source..
If you are using two data sources in the same workbook then make sure that the data blending happening correctly or not.?
The data blending can happen on the Server data sources or local data sources in the Tableau desktop
Please share more insights on the problem you are facing ..so that we can help you better..