There is nothing wrong with the code 4 Form 1099-R. Code 4 means that a distribution from your deceased father's IRA was made to your mother as beneficiary of your father's IRA, not that your mother died. TurboTax asks the RMD question because, if your father did not complete his 2018 RMD before he died, the responsibility to complete his 2018 RMD falls to your mother. It asks this question to make sure that your mother did not roll over to another IRA in her own name any part of your father's RMD for 2018.
