Did they reset the gearbox adaptions??
The ECU 'learns' the required modulation of the valves to attain the best shift transitions and amount of slip etc.....as the clutch plates wear, the required modulation times change and the gearbox adapts to these requirements.
With a new box with new clutch plates, amount of valve modulation required will be different to what the ECU has 'learnt' and need to be reset so it can learn again.
If they have been reset, it could be the ECU is re-learning which can take a couple of hundred miles or so until it shifts smoothly and the clutch packs are fully bedded in.
But, it does sound GB or TC related......but also get them to look at the engine mounts....on the Td6 L322 they are 'active' and are hydraulically controlled....if they are leaking and loosing pressure, engine knock and vibration can be transmitted to the subframe and subsequently cause vibrations.
