You are correct to say TurboTax calculates automatically.
TurboTax does claim amounts by how you answer the questions in TurboTax software. Therefore if you have entered amounts and clicked on yes, where it should have been a no- Then TurboTax will calculate by answers given.
For example - in your case- you thought you could split his US pension and CRA says no you weren't entitled. You thought you were so while completing your income tax return you would have put "YES" I want to split my husband's pension. This is where the error occurred.
Please read the following on how you can split pension income
If you feel that you did complete your income tax return correctly and that it was TurboTax software that made a mistake - please reach out to our support team for help- https://support.turbotax.intuit.ca/contact/
