mine won't down shift in to 1 when you come to a stop after the tranny is worm . but can be manually shifted and works fine and hang up a little before 4
Im thinking you dont have any problems with your transmission, but that you just have a really tight converter(low stall speed).
I have one of Goerends tightest converters. I was probably around 300hp in this video. You can see it is slow to spool. Im still running the same converter, but i plan to go to a looser one when i build my transmission one of these days.