Is the IRA/SEP/SIMPLE box marked on the form provided by the financial institution?
Code 4 would be used for distributions from a traditional IRA, not for distributions from a Roth IRA. Apparently there is disagreement between you and the financial institution as to whether these are Roth IRAs. For a distribution from a Roth IRA paid to a beneficiary, it's more common that the financial institution use code T instead of code Q, leaving it up to the beneficiary to assert that the decedent had met the 5-year requirement for qualified distributions.
A distribution from a designated Roth account in a qualified retirement plan (not a Roth IRA) would have code 4 but would also have code B and the IRA/SEP/SIMPLE box would not be marked.
