Which tells me it's something other than software. If software is bad, it's bad. Mechanical things on the other hand will happen at any time.
Mine was like a light switch too. Perfectly fine until 15k, started acting up and got worse and worse. In my case I'm hoping it was the erratic MAF that might have damaged the DPF. They're replacing the DPF this week. What may be interesting is if it seems to fix it and then does the same thing around 15k.
It's rather unlikely the software changed itself at 15k.
My idle time is just over 7%, WAY less than almost anyone on the list so that's not it. Also towing is at 90%. I'm towing around a 15k 5th wheel toy hauler with maybe 20% in mountains. The DPF should almost always be hot enough for passive regen yet it still failed.
I can only think of three reasons the DPF would plug up if you're not sitting around idling all the time. Too much fuel, too much oil or the DPF itself has a high failure rate due to design or poor construction. Too much fuel likely points to a sensor or injector fault, too much oil likely the turbo or the engine itself.
Can you think of anything I've missed here? I'm much more versed on naval propulsion systems than auto diesel engines but the troubleshooting process is the same. I honestly don't believe Stellantis has no idea what's going on. The world's worst manufacturer could figure it out in the two years these have been giving the same trouble.