Did you ever find out the problem?

I suspect the governor.
But the only way to find out is either pull the gov'
or it wont show up in the fluid in the pan.
You have to pull the plate between the front valve body
and also pull the rear valve body to get the plate off.

I've read were (after pulling those), a forum member,
pulled two small thimble looking screens from the rear valve body
and one was clogged.
And that solve his shifting problem.

But if you find long thing shavings once you drop that plate
then it's likely from the gears of the gov'.

I think you can partial drop the tranny (referring to MBZ not sure about Porsche) to pull the gov.

You may also have to remove the tail section of the tranny
to replace the other heli gear that goes on the main shaft.
Typically it damages both gears not just the gov.

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