Any time I encounter the "Calculation_####" error in Tableau, I've been instructed to remove/delete the extract and re-create it. This has solved the problem for me every time, but I'm not connected to Excel files so I'm not sure if it is any different for you.
Similar instructions given for fixing this error: "Ignoring calculated field, field is already defined by data source" Error | Tableau Software
Also, note that your thread is marked "Assumed Answered" so most people will skim right over it since they believe a solution was found.
Cheers, and best of luck. Did you contact Support with this?