EDIT: After posting this, I realized that the ProSeries final review indicates that the return is not eligible for e-filing. This is very frustrating, as the software appears to now properly allocate the Section 1291 taxes and interest that I enter in Forms 8621 to Form 1040. How many years does it take to get a form and an attachment to work?

The Form 8621 in the software has improved. The Sec. 1291 tax that I calculate and enter on the Forms 8621 flows to Form 1040, Line 16, and the  interest flows to Schedule 2, L. 17p., and everything seems fine. The attachment function for Form 8621, "Taxation Of Excess Distribution Statement", however, has quirks. When I click Quick Zoom in Form 8621, Part V, below Line 16a, to create statements for the different Forms 8621, I can create a statement and give it a name and select it as if I were linking the form to it, but this does not appear to be an exclusive link. With two forms 8621 with excess distributions, I see both forms every time I click Quick Zoom on either form. When I try to e-file, I get the following error message:

Return Rejected 11/13/2023
Code: F8621-023-02
Form: 0(00) Form Copy:
Line #:
Description: 2778(/efile:Return/efile:ReturnData/efile:IRS8621[1]/efile:DistriAndDisposOfStoc

Error Detail:
If Form 8621, Part V, Line 15e 'TotalExcessDistributionAmt' or 15f
'GainLossFromDisposOfStkAmt' has an amount greater than zero, then "Taxation Of
Excess Distribution Statement" [TaxationOfExcessDistributionStmt] must be attached to
Form 8621.

Should I be able to e-file this return? I know it wasn't possible in prior years. Is there a way to override the attachment error? As mentioned, the tax return numbers seem correct otherwise. 

Strangely, if there are only losses on Part V, I am able to e-file the return. No attachment is required, and the loss only appears in Part V with nothing flowing to Form 1040.