I have the same issue with Return/ReturnData/IRS1116/ForeignTaxCreditSource/ForeignTaxesPaidOrAccruedDt
I noticed that the form expects the date as mm/dd/yy, but TurboTax enters it as mm/dd/yyyy (e.g. 12/31/2020). There seems to be no way to overwrite the format used by TurboTax to give it a try.
