This is a common problem on all 722.6 gearboxes the problem is that the RPM jumps up a little, when shifting under load.
On original Mercedes cars, this is not a problem as power is limited during shifts.
On my controller this issue can be handled without doing any modifications to the gearbox.
As there is a setting that only allow shifts from 3 -> 4 if TPS is below an adjustable value.
If you wish to shift at higher loads the following modification might very well be necessary
Found this video on YouTube, at around 9:00 minute how to snap off cunductor plate
First remove the valve body from the gearbox,
1. Remove oil pan
2. Pull out electrical plug
3. Remove electrical socket, with 8 mm socket and pull out, make sure the two O-rings are intact.
Remove all bolts holding the valve body
Remove the plastic covers for the solenoid valves, and the bolts holding the solenoid leaf springs.
Now solenoids can be pulled out,
Remove the conductor plate, pull straigth up.
But be careful. one place there is a hook, and you have to pull straigth up at this point, to avoid braking it.
Now remove all the bolts and separate the valve body.
Here it's separated and you can take out the plate between the two valve body parts and drill it.
I have drilled mine to Ø4 mm.
If you do this modification, you have to adjust a little to get the best out of it
Goto "Shift Firmness" ->
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
"Firm/Load 3->4" 0 0 -2 -2 -2 -3 -2 -1 0 0 0
"Firm/Load 4->3" 1 0 0 0 0 0 0 0 0 0 0
Do i have to say keep work place clean, and no dirt in the valve body ;-)
Credits to Drake for sharing this solution