I've had my smoker for about 4 yrs, One of the first before they started having problems. The last few smokes I've noticed some wild temp swings 10-15 degrees sometimes 20. If I set it at 250 will run up to 265 then shut off untill 240 back up again. It's digital so can't attribute it to anything tangible. I had a bradley before this one which wasn't a digital and used an Auber PID on it which worked great.
I read about a mod here, the person unhooked the element wires, fabricated a cord, hooked it to the element and ran it to the their PID. I went rummaging thru my junk closet and found the Auber PID (it's a 2 probe) and hooked it up to the cord I'd fabricated. The display still works on the MES just doesn't control the element any more, you can set the timer, turn on the light and use the meat probe. Ran the auto-tune and then set the temp on the PID to 250. OOPs l left out a step I drilled a hole near the original temp control on the back of the MES and installed the PID temp sensor.
Using the the MES meat probe, the Auber meat probe, and a stand alone meat probe I put them in within 6" of the Newly installed temp probe, the auber probe and the stand alone were within 2 degrees of each other, the MES lagged behind 4-5 degrees. Once up to temp the Auber kept the temp within 1-2 degrees of set temp, I,ve always wanted to set my sauce on ribs at a higher temp and was restricted to 260 on the MES., I ran the temp up to 350 with no problem so I was happy with that. Before someone cautions me I know I should monitor the smoker when at 350 and only use it for short periods but it will work for the ribs.
The Auber PID's aren't cheap at a little under 200 but if you're serious about your smoking this is the way to go if you can justify the cost.