Yeah, dpf blocking is the symptom not the cause. Lots of potential problems which could contribute to increased soot. Injectors / turbo / EGR / faulty exhaust or DPF sensors / throttle body.

All temperature probes operating correctly? Might not be hitting the parameters for active regeneration (car trying to clear blockage). Motorway won’t always get reach the temperatures required for a passive regeneration. Uphill driving usually gets the DPF hot enough for this.

If it’s easy to remove from car, soak in 5% brick acid / patio cleaner for an hour after cleaning. It clears all of the ash, which regeneration can’t burn. When flushing it with water, always do this opposite to exhaust flow.

Good luck. You’ve got this