if problems with dome thermometers are common? Bought a new XL two weeks ago. Finally fired it up last night. To my dismay temperature didn't rise above 100 for 1st 30 minutes. Finally got it as high as 375, never above, after lightly tapping on thermometer. Very disappointed and thankful I didn't have a patio full of people for this 1st run. Are problems like this rare with new eggs?