A few more questions. Not trying to beat a dead horse, but to see if we can help prevent further issues.
Did you have a temp probe in the cabinet itself? You can search this site for the procedure to verify the cabinet temp. It sounds as if the cabinet temp may be significantly higher than the dial position indicates. How new is the smoker? Did you inject the bird or not? I assume the bird was not stuffed. Correct?
4.5 hours sounds extremely short to me for that size bird.