You'll need to submit a substitute Form 1099-R (Form 4852) using the correct code (code J only), and provide explanation.
Because the requirements surrounding retirement accounts are so complex and subject to misinterpretation, I've simply been studying IRS documentation regarding retirement accounts (among other things, the instructions for Form 1099-R) for about 15 years. I've been a TurboTax user for about 30 years.
