@CarissaM @SForrestLO My TurboTax (Deluxe CD version on Windows) updated today to 572 with no improvement. I went through review and federal-only efile again and got the same error.
I've now made the payment for this amended return online via EFTPS, so I don't need to finish filing the amendment before the April 18 deadline. I'll wait a little longer to see if TurboTax can fix the issue for amended returns before I give up and file on paper.
Given the other posts here it seems like the error is probably specific to amended returns only. Maybe after the main filing deadline passes on Monday TurboTax support and developers can put more attention into amended-return issues.
