dd15 dpf regen problem

hi everyone please share your experiences and knowledge about my problem.
a month ago i had regen every 300 miles, took it to a shop cleaned the filters for $550, connected to computer,performed regen and lights on dash didnt go away ( check engine, stop engine and flashing dpf) tried to regen at least 5 times, no change. ... ash soot level was high according to computer. thought it might be the sensor and replaced with a new one. no change again. took it to another mechanic nothing found. took it to another mechanic and performed regen, boom!!! lights are gone now. took a load drove 800 miles then again... short story long i still have the same problem and what can u guys recommend? im thinking its the doser injector.. can it be? thanks in advance

 

when we connect it to the computer everything looks normal no code but it needs a regen because ash soot level is too high. thats the only thing i can say about the code and also sensors read 580f 1000f+- 1000+- for readings of the sensors

 

im not sure about the hours on engine since i dont have access right now but i have 2010 cascadia with dd15 that i have been doing pms every 3 to weeks. also i dont know the brand of the dpf but i can tell you that i dont have def, so only dpf. my mechanic took the filters out and send it to local place to get it baked and according to the people who had done this, my filters are in great condition. theres one thing im saying it might be the doser injector bc sometimes when i start the truck, fan blows a coolant smell ???

 

that's exactly what i did my friend i stay away from freightliner dealers as much as i can since last time i had very bad experience with them

 

pfff thats expensive if thats on the filters but i heard full system for cascadias are going around $12k

 

one more question, have u changed it by urself?