First the IRS is not always correct but if they are and TT made the error then put in for an accuracy guarantee. Sadly most of these errors are made buy the user ... if you didn't complete the entire 1099-R section and correctly answer the questions then that was not a program error.
Any calculation errors on the part of TurboTax are covered under the Accurate Calculation Guarantee. TurboTax will pay any penalties and/or interest due to a calculation error but not any taxes owed. The Guarantee does not cover any user entry errors or omissions.
See this TurboTax support FAQ for the 100% Accurate Calculation Guarantee - https://ttlc.intuit.com/questions/2566201-what-is-the-turbotax-100-accurate-calculation-guarantee
See this TurboTax support FAQ for submitting a claim - https://ttlc.intuit.com/questions/1901269-how-do-i-submit-a-claim-under-the-turbotax-100-accurate-ca...
See this TurboTax support FAQ for documents needed to submit a claim - https://ttlc.intuit.com/questions/1901060-what-documents-do-i-need-to-submit-a-claim-under-the-turbo...
