How could meat temp be dropping?

I've got a 3.5 lb boston butt on my UDS. It's been on for 9 hrs at a steady 230-245. In the last half-hour, the meat temp has actually started to drop. It was at 190 and now it's at 180. I have no idea what could cause this...

Thoughts? Help!

I have cooked a lot of boston butts at home and in bbq competitions and this has happened to me when the temp. of the smoker is too close to the temp. of the meat. I like for my butts to be at 200 when I pull them so I usually have to have the smoker temp. at 250 to get them there. Try raising the temp. of the smoker to at least 250. It should do the trick.

I have taken readings in several spots. I didn't know that the temp of the rendering fat actually drops.

The chamber temp is read from just below the meat (clipped on to the rack).

I bumped it to 250 and have my fingers crossed. Thanks for the help, fellas.

When the temp breaks up, it will hit target temp pretty quick. Don't let it sit in the pit for too long after the break or the meat will start to get mushy.

Kothe..................;}-

You've got the pleatau goin' on... it'll rise again in a bit. Just drink some more and tell somemore lies. This happens a lot on Pork Butts and Briskets.
I don't know the 'scientific' explantion for it, but undoubtedley someone with that info. will show up.
I put it off to God; God likes us to use his creatures for food and cooking it like we do is his favorite(ie-burnt offerings to Him). Now it was unsaid, but I know some Jewish Women and if you went to throw a piece of meat away, well let's just say it didn't go to waste.
And , God gave us the skill to brew Beer, so that's why when you are "Queing" something and it pleataus, sit back and thank God for the time.
Be good and
SMOKE HAPPY
Stan aka Old School