No DPF is designed for short trips, short trips or wrong oil is a death sentence for a DPF.
On modern diesels injectors are coded individually to the
ECU and they have specific injection quantity values per injector programmed into the
ECU.
If one was leaky it would throw a code and run rough.
I'm calling BS on their excuse and its either wrong oil or city driving.
All the ones I saw come through my workshop were those two reasons.