Any way you can share a packaged workbook?
What happens if you create a view with FieldOne, FieldTwo, and the calculated field side by side? Would you be able to share a screenshot of the results of that?
Is it possible you should be aggregating? I don't think it would cause this issue, but you might try
If this, or Joshua's reply, doesn't help, please post a packaged workbook example. You can copy and paste a subset of your records into Excel, remove/revise any sensitive data, pull into Tableau as an extract, and post the workbook here. Doesn't take too long with a bit of practice. Cheers!