Idle Cutting & Partial Load, 4th & 5th Gear

Hi everyone, my Audi 80 TDI 1Z, manufactured in 1994, is experiencing the symptoms described above... the shaking/jerking stops when the speed signal is disconnected.
I'm pressing the button on the turnout control panel, and I've already tried a few resets, but unfortunately, nothing has worked. Has anyone ever opened this turnout control panel (HDK) before? If so, could you tell me what's important to look for? Thank you in advance!

Best regards, Manni.

Have you ever used the search function?

Then you would have found this.

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