I have just uploaded my first data source (google sheets) and workbook online since moving to 10.4, and following its first refresh all of my tables change to display incorrect data.
For example, our sales 'this month' are 43, but change to 49 when the extract refreshed online. When I downloaded the data in excel, it appears the date format for some entries have been switched from 'dd/mm/yyyy' to 'mm/dd/yyyy'. This means a sale that was entered on 11/4/17 is now showing in this months figures with a date of '4/11/17'. There are still some showing this month that were entered this month so the error isn't consistent.
I have another data source from the same google sheet published in previous versions of tableau which are working fine and displaying the correct information.