With 1040-x you can't change the original amount specified to be applied to next year.
in any case, that setting zero or non-zero in your revised return does not change the amount of overpayment shown on your original tax return.
It's not clear to me what is causing your error.
if you want to apply another overpayment with 1040-X to next year, that amount has to come out of 1040-X Line 21.
@gustj012
