Volvo XC90 (2006) Auto, Diesel, Geartronic

Despite recent auto fluid change, the car "dithers" in Drive, note; the garage (in Spain) did not change the filter, they would only do oil change.
Finding a garage here in Spain with the technology and experience to carry out detailed repairs on this Volvo is almost impossible.

(If I use the manual change gearstick instead of "D", the problem is considerably less but still apparent).

I am wondering is the gearbox on it's last legs or is it something relatively simple that someone with the knowhow could fix.


Any suggestions would be most gratefully appreciated.