@ML50 wrote:
I spent at least an hour with customer support trying to address this before the specialist concluded that this is a bug in the system - she said the signed form 8453-FE would be attached, even though the preview does not show it to be...
That is correct; the 8453-FE is attached separately (after it is printed, signed, and scanned) from a file saved on your computer. The list of forms displays an unsigned 8453-FE.
Provided you followed the instructions for the attachment of the 8453-FE, you should not have an issue with your return being rejected for that reason.