'12 Pete 587 Won't Regen

As the title says I have a 2012 Peterbilt 587 that has it's moments where it will complete a regen but it takes days of trying for it to complete a regen after failing a few times. I had taken it to a Rush a few months ago but whatever "fix" they did only lasted for a few months. I am hoping someone can lead me to an actual fix over something that clears the code for just a few months.