A4 B6 multitronic doesn't recognize P/N when warm

[BKrebs]

Hey.

I have an A4 B6 multitronic from 2002 that is starting to act up.
It seems that when the engine is warm I am unable to start the engine because what is controlling ignition does not recognize that the gearbox is in P. Furthermore P or N is not lit up in the instrument cluster, D and R is working fine.
The gearbox itself engages P an N just fine even while the instrument cluster doesn't show it.

I made a video where I'm parked and in P after a long drive on the highway. First the engine is off and the fault is present, after a while it cools and P is suddenly lit in the instruments. I turn on the engine, rev it to warm it up and the fault comes back.

https://youtu.be/DXDvmrRnRBs

And there are no fault codes stored.

Do any of you know what could cause this?
i have read a bunch of forum posts but no one seems to have the same fault.

[BKrebs]

Cupramax said:

Sounds like the gear position sensor which is in the Gearbox ECU. You might not have wanted to hear that...

That was what I was afraid of.
So from my understanding I will have to change the whole ECU, is that correct?