Austin XL temp control problems

[oldsmoke]

Hi,
I have a Austin XL with a Smoke Daddy PID controller
The smoker can not get down to 225F. it will happily sit at 300 at any controller temp under 300. Above 300 controller temp it will control it reasonably well.
I can crack the door open ~1in and i can get down to 225.... so it seems like a airflow issue

anyone have this issue?
Thoughts?

 

[oldsmoke]

other info:
i do have a heat diffuser over the fire box, but i don't see why that would affect this

 

[Bigboss]

Mines doing the same. Did you figure it out?