Temperture not holding

Best bet would be to talk with Bill or Tony at Cookshack tech support Tuesday morning.

As usual,follow Max' advice.

I'd use an alternative therm to check it as it cooks,and turn dial to around 225* on my alternative therm and work with that.
Your cooker cooks moist, and probably doesn't cook much past the 250* and will probably do it's usual fine job.

If all else fails,every hr poke the brisket with a two tined meat fork,until if feels done.

That cooker was one of the best brisket cookers for a half century,before anyone heard of a therm.

Enjoy the finished product.

you purchased it 3 years ago and you're just NOW stopping by? Sorry, just glad you're here now.

Did it stay at 250 or was that the high point? Have you been tracking the temps before and does it always overshoot.

These smokers have a tendency to cycle and if you caught it during one of the cycles it's possible you were just at the high point.

What were you using to verify the temp, an external thermometer? Maybe just check it's accuracy also.

And of course, call CS today, just have some more details for them and they'll help you out.

Stop back and let us know what they said.