What about the fan? I can't see any in the picture. If you have a general one that blows over the heatcore, that's not actually a good setup.
Did you check that the set screw holding the stainless steel barrel is tight? Eventually, unscrew it, take the barrel out and check if the surfaces are clean and there is nothing impeding the thermal transfer. Make sure both surfaces are clean and smooth.
Did you check that the set screw holding the stainless steel barrel is tight? Eventually, unscrew it, take the barrel out and check if the surfaces are clean and there is nothing impeding the thermal transfer. Make sure both surfaces are clean and smooth.