My son's reply to the problem of the thermometer in the smoker dropping so quickly:
Hmmm - I just use the smoker thermometer, not a meat thermometer. I would think the same thing the poster said - his thermometer was getting an internal air temp rather than a meat temp.
"I'm that fond o' my fiddle, I could sit in the inside o't, an' look oot."-- Peter Milne, famous Scot fiddler