Need help, my very first batch. Put into smoker 5 tubes 21/2 x 18. Started at 120. Then at 140. Started at 10:30am. Been at 160 smoker temp for last 4 hrs. Internal temp is at 142. Turned up to 170-175 at 9:30 pm. IT is at 145 at current time 10:15pm. Is this stall common?