The 7 speed DSG used by VAG is not a box that any same person would recomend. It has a torque limit of 250 nm which is exactly what the 1.6 TDi produces.

Have you had the car form new? If not did the previous owner fit a tuning box or have it chipped or remapped. Any of these will shorten the life of the gearbox.

You have 3 options in reality

Carry on as it is and hope its not a terminal problem

Sell it and buy a manual car

Take it to a Seat dealer and hope they can get some goodwill for the rebuild form VAG but it could cst you £££££'s. If the car has not been VAG serviced forget the goodwill even though the oil was changed under the recall.

If you must have an auto and a diesel the 6 speed in the 2 litre VAG cars is much more robust.

The petrol 1.4 are a truly great car in manual form but also come with the 7 speed DSG making them a poor buy.

Auto boxes in small low powered cars are the work of the devil in most cases and are best avoided.

Heard of a similar problem on a golf gti mk6. It involved weard out clutches.

Now, another golf, this time not the gti but still petrol had the same judder and wasnt the lucky. Mechatronic unit faild beacause of metal shavings in oil, so they avided to put new mechatronic sistem in it and replaced the whole gearbox.