I think I stumbled onto the solution here. The problem is you have to know the solution before you cause the problem! This is what worked for me:
DO NOT VISIT THE K-1 SECTION OF THE INTERVIEW UNTIL YOU HAVE **IMPORTED** THE TXF FILES!
Yes, if you import the .txf file before you even give TurboTax the chance to ask you if you want to deal with your K-1's, TurboTax appears to correctly import the .txf file, then later merge the carry-over amounts from the prior years correctly.
I have always delayed dealing with the K-1's until the very end. DON'T! Because this year I happened to visit just 1 K-1 prior to importing several, and that was the only K-1 I had to copy numbers to do a manual merge. My other 2 appear to have worked perfectly.
Now, if we could just get TurboTax staff to insert a question to the user prior to reaching that section of the interview "Have you already imported your K-1's?".
