Pit Temp Probe Position

I don't use those things nor will I ever, but I can tell you if the tip of that probe is to close to cold meat it will give you a false reading.

Hang it through top vent until meat gets some temp in it. Putting it close to cold meat will give an inaccurate reading.

What are you comparing the temperature of the Digi-Q reading to?

Or are you trying to say the temperature of the pit never rises high enough to reach the programed pit temperature? If this is the case, check the following:

Double check the pit / meat probe settings and make sure they are plugged into the right ports.

Make sure the slide on the bottom of your fan and / or ball valves for the air from the fan are fully open and not obstructed.

Maybe the CFM of your fan isn't enough to allow you to get hotter temperatures.

I have the DigiQ DX2 and find it to be totally accurate.

To answer your other question... I keep the clip greater than 1" from all meats in the cooker. when I have a large load, I have a stainless 6" 1/4" rod attached to another clip so that i can get above / below the meat racks to attach the clip for the pit probe.

Also note that lump charcoal will burn hotter and cleaner than most briquettes, try switching brands of charcoal.

I ignore my cookers thermometer even though it is a tru-tel. With the DigiQ DX2 I set the temps and walk away. It even ramps down the pit temperature as it nears the targeted internal temperature of the meat to prevent over cooking so I can determine when the meat is done by probing, twisting, or bending. It is simply a tool to control the pit temperature in my absence, but it is a very good tool which allows me to sleep very well on overnight cooks.

Is it possible that fat/grease is dripping onto the thermometer? If so, some evaporation from the thermometer could be lowering its temperature a bit.

That said, I've found that temperature can vary by quite a bit inside the smoker. Two thermometers a few inches apart read temperatures that are 30 degrees different. Using a diffuser helps quite a bit.