This ^^^ is for real.BladeAndStone wrote:Not sure if you are noticing a drop in temperature within a few seconds to a minute of loading in the Portafilter but there is also something called heat sinking which can occur to the group (and therefore your brew temp) if you are loading in a cold PF into the group. The cold PF will "steal" heat away from the group and can lower your overall brew temp. So attempt to keep your PF loaded into the group when not in use and see how that impacts your results.
It's one of the tricks we do on our Pavoni levers to squeeze out an extra shot before it starts becoming too hot, in case we want to do more than two. Putting in a cold PF, refrigerated or even frozen, really sucks down the temp. This is good for us Pavoni users, but probably bad for the OP.