Here is the real deal that is going on. I have been through everything with these trans and done quite a bit of investigation.
So it turns out that ZF and for that matter Ford (6R80 is an exact copy of the 6HP26 under license from ZF) as well stuffed a 6 speed trans into a 5 speed case. How do you do that? You make the clutch packs smaller. Well, what happens when you use smaller clutch packs? They wear way faster and have issues sooner. That is why they did away with it.
As it turns out the valve bodies or mechatronic units are failrly fast at switching gears. When it detects slip it switched to the next higher gear to prevent damage,etc. So this causes bumping. Sometimes its the 2-1 and sometimes it happens on other gears or clutch packs as well. The mechatronic units also fail at a high rate and require replacement. See www.thectsc.com
as they have had the best prices that i know of.
To alleviate the bumping down low, ZF came up with a software update that BMW and Ford both use that maximizes the pressure in the transmission, holding the clutch packs firmer to stop slip. Every person who has had this 2-1 tip in done says the transmission feels as it is loaded all the time and acts differently. They are right. The 2-1 tip in will fix it, but at the cost of feel and possibly longevity.
Here is what i did in order
(1) Update normal programming
(2) Program for hard shifting (+HADS)
(3) Replace mechatronic unit (Some symptoms resolved, some still exist)
(4) New Fluid / Filer / Pan / Mechatronic Sleeve
(5) Remove +HADS from VO, Reprogram normal
(6) Program 2-1 Tip In (+21TI)
Car is now drivable but the feeling is different and some bumping exists, much better than before as It would bump / slam in all gears,