I used my Forster for 10 years, great press, but I like my RCBS Summit and Mec Marksman better.
Less run out with both of them over the Forster.
I know nothing about your preferred presses, or your methods or dies and shellholders. And I'm NOT questioning your statement, you know what you know, but I wonder if one of your shell holder plates is binding or even bent (even though they are hardened). I have two Co-ax's, one dedicated just for 6.5 match competition...the only bad runout I found after many years could be traced to other causes, one a crookedly drilled and tapped die lockring and a tiny lead pellet trapped under one shell plate, probably from loading snake shot for a pistol.
