Very old post but did you ever find what this issue was?
I am having the same issue with my e34 540i has only done 82,000kms, drives fine through all gears when light footed but throws trans code and goes into limp mode and holds 3rd gear once you put your foot down.
If I turn the car off and wait 10seconds and restart it's ok until I put my foot down hard again.
I have pulled sump, valve block stripped and inspected. The plastics check valve balls are in good condition with no wear etc...
Any help will be much appreciated.
Thanks.
