Thank you for all this dialogue. In my case, both a 5329-t and 5329-s were generated even though both of us are well over 70. Oddly enough, both of them had my wife's RMD on Line 2-L. Neither of our 1099-R forms have a code U in box 7; rather that box has a code 7 and the IRA sub-box has an X. I have not experimented as you have with different ages. I did use the step by step. The presence of the 5329s doesn't seem to change the tax, as expected.
I'm reluctant to delete the form as I wonder whether that will result in some hidden box being checked to reject the return or trigger an audit.
This is definitely a bug.
