Problem Audi A4 - Speed indicator problems


Hello everyone,

I have a friend who has a 2001 A4 that had a broken gearbox.

Changed it but the mechanic hit the sensor on it.

They installed the old one, but the dashboard no longer shows the real speed, the needle goes up to 50 km/h and gets stuck there

whatever the running speed.

He changed the board, but nothing, he changed another sensor and the same.

Can you help me with an advice, where the problem comes from, and if it can be solved somehow.