Hi,
same problem with my ultimaker 2. Unfortunately. After almost 2 hours of gently trying to remove it by heating up the nozzle at different temperatures i give it up finally.
Next question is where to go from here? Cut the sensor and replace it? I have no problem releasing the heating part.
I admit, the nozzle is a mess with burned filament but as i learn here, this is not something unusual to happen. So i agree, its a design flaw to make these parts that are easaly worn out to be so hard to replace.
Herman