Did those use DEF? We had 274 Macks with tons of issues with the regen systems, I think they pawned them off to centers.
They used DEF.
Mine did have an occasional Regen issue. It would derate once in awhile and have to be manually regened at the shop using the computer to start it. Our mechanic finally tracked down the issue.
It was either a NOx sensor, or another DEF related sensor that he replaced and it fixed the issue. It had been going on for almost a year until he tracked it down. I think the part cost almost $2000.
It was a 10 speed, not auto, which I didn't mind, with no bells and whistles, no beeping and buzzing, but with air bags instead of springs.
Rode like a Cadillac