I don't understand. Exception code 12 is because you told TurboTax that you had an exception.
In the screens after you entered the 1099-R, did you enter a number for "Incorrect Early Distributions"?
Step back though the 1099-R interview and see if you indicated any exception (TurboTax doesn't make exceptions up).
Worst case, there is a number trapped in your 1099-R but you can't see the screen to remove it. The fix is to delete the 1099-R and re-enter it.