I've had 4 sticks of summer sausage in the smoker for 10 hours now. Started at 160 and slowly raised temp to 175. I'm using an electric smoker with a pid controller. Internal temp of meat was gradually going up until it hit 145. It stayed there for a couple hours then started dropping. It's now back down to 138. Not sure why it is dropping. Double checked smoker and meat temps to verify they are accurate. Any ideas? Didn't experience this with the last batch I made so I'm a little confused.