Is your dome thermometer accurate?

Best way to check is pull dome thermo out and put the tip in boiling water

Grid temp is usually different than dome, on indirect cooks its usually lower, direct higher. If your thermapen was not in the shadow of your indirect piece (plate setter, stone, etc) it will typically be higher than dome. To check your dome thermo for calibration, boil some water on the stove and remove your dome thermo and check it in the water. Should be 100*C +/- based on elevation. There is a but you can turn on the back of it to line it up if its off.

Heat rises, so dome temp will generally be 20 - 40 degrees hotter than grate temptemp but have tried calibrating the thermometer. thermometer it should read opposite of what you're getting

This post is wrong. The hottest part of the Egg is where the fire is. There is a temp gradient where the minimum temp will be dome. It does not matter that heat rises. If you take that thinking to the extreme, it means that the dome will be hotter than the flame. Clearly impossible. My dome temp only comes close to matching grid temp, when steady state occurs. Meaning the lid closed for a significant time. Otherwise grid is always hotter than dome,