EKO 25, keeps going past 180

I keep the controller set at 180, but the last few days, it keeps going past 192, an a couple time to 201. Any ideas why this is happening? Do you think I may have a faulty temperature probe?

Is the fan shutting off at 180 and then it slowly creeps up to 192? Or is the fan staying on?

The fan is not staying on past 180. As a test, I started a burn from cold, an still seems to bring the temp up way past 180.

My boiler does the same thing. Fan shuts off at the set temp but then it creeps up. I think it worse on warmish days. Think about when the house is calling for heat the fire is cranking and then the house stops calling for heat, well the fire doesn't instantly stop (like a gas boiler). I have a sensor installed that opens one of my zones as a heat dump if it gets a little over 200. And that dump happens on a pretty reg. basis. I chose the bathroom zone because a toasty bathroom isn't too bad.

Yes, actually, it was on the warmer side I yesterday, and I also have a small Modine heater setup as a a place for the heat to go when it get's over 200. I'll keep an eye on it.

It is not unusual for this to occur. The only mechanism that stops draft from flowing through the boiler is a small counter balanced damper on the inlet which could easily be overcome by a higher draft. With very dry wood and higher draft that can occur when the weather is cold and clea,r the coals within the fire chamber can continue to glow, giving off enough heat to raise the boiler temps if there is no call for heat. There could also be a small leak in a door gasket allowing air to enter the firebox.
Like easternbob, I have a mechanism that doesn't allow my boiler to overheat. In my case, I have an aquastat that launches a circulator when the boiler temperature reaches 185 and pumps boiler water through a coil in the bottom of my unpressurized storage tank. It also serves as a second circulator that launches at the higher temperatures, keeping my boiler from idling when storage temperatures start approaching boiler temperatures.