russg, some questions.
• How old is your MES?
• Have you been successfully using your MES for a X number of smokes before this problem?
• Were you using an extension cord?
Older MES units had problems with the wiring and connectors in the back. Depending on your model there may or may not be an access plate in the back to the connectors for the heating element. If you have a model with access plate inspect the connectors inside. If you have no access plate, you will need to drill out the rivets and inspect wiring and connectors. The newer models are suppose to have heavier gauge wire, most who did this fix upgraded the wiring to 12 ga high heat, and some changed the connectors, google this forum the fix is listed several times.
Extension cords need to be 12 gauge, some use a short 14 ga, but why wonder just get a 12ga it could be 50' long if it's 12 ga.
If you are going to cycle off (reset) your MES, the correct way to do it is: Turn off the MES using the MES controller on/off, unplug the electrical cord, wait a few seconds plug the cord back in, turn on the MES and reset your temp and time. Over the years I have had to do a reset about 6 times. Sometimes I just do the reset after my preheat and after I have loaded the meat and water tray, then I do the reset and start my smoke, its just a precautionary (probably unnecessary) step. However if you walk out after an hour and the temp is still sitting at 170-180º and you have a normal load, experience that a few times and you know why I just do the reset as an extra step.
If you are still having problems, and know how to do an amp reading, check the amp draw. There are plenty of websites that explain how if you are not familiar.
Of course a call to Masterbuilt helps too.