2018 Freightliner Cascadia DD15 - Recurring SPN 3251 FMI 0 (DPF Pressure High)

I'm fighting a stubborn issue on my 2018 Cascadia. I keep getting a high pressure differential across the DPF. It will trigger a parked regen, finish successfully, and then the code comes back within 200 miles. The soot level stays low on the gauge, but the pressure sensor says otherwise. I checked for exhaust leaks before the DOC and everything seems tight. The truck has 450k miles on it. I'm worried the DPF is baked or there's an upstream issue with the 7th injector (hydrocarbon injector) not getting the temps high enough to actually clear the face of the brick.