TurboTax only generates a 50% excess accumulation penalty if after clicking the Continue button on the Your 1099-R Entries page that you were required to make a RMD of some amount by you received none of it and you are not claiming a waiver of the penalty. Either revisit that section and modify your answers to indicate that you received all of your RMD in 2018 or delete the Form 5329. To delete a form in online TurboTax, go to Tax Tools -> Tools -> Delete a form, then click the delete button on the line for Form 5329.
If you are married filing jointly, make sure that all Forms 1099-R are allocated to the correct spouse.
