When keeping it real goes wrong.
We are only printing high temp on the left as its recommended by Bambu due to brittle filament and the left has a bigger tube bend radius. Our prints are functional so there generally only one color. The right nozzle is not used but still has low temp filament in it(not loaded but left over). This is what we think is causing the issue.
I just did a high temp print with the left nozzle and switched both nozzles. Right nozzle was empty and i did a cold pull on it. After the.print both nozzles removed easy.
ABS, ASA and PETG are all quite evaporative, eventually it would condense on the nozzle hear and there.
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Fundamentally, I agree with @StreetSports : if there was better surface contact between the mating surfaces, then this would be a non-issue. Seems as though some of the nozzles in the photographs have little to no issue, whereas some appear to have had a lot more.
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Meh kindaā¦ I stand by my original point. Dude got lucky 
I had printed mostly petg with the right nozzle, so the outcome fits your observation.
Same, I print exclusively PETG
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In the event @StreetSports is correct about some of the mating surfaces being a bit too loosey goosey, I notice that there is a replacement right-hand hotend heating assembly:
A different version is also sold for the left hotend.
From what I can tell looking at my nozzle. The rectangle sensor in the back sticks out a little past the rest of the heating assembly. Not much but just enough to have a very small gap everywhere else. I think this is by design to make sure the sensor has a full mating surface. Like everyone else, I think its due to using a lot of PETG HF in the other nozzle. PETG HF vaporizes more than other filaments. Iāve done about 10 prints so far where I swap the right nozzle out for another nozzle Iāve deemed to be HF (the stock 0.4mm standard nozzles that only get high temp filaments in it) and the problem went away.
So Iām fairly certain its due to printing high temp in the left nozzle with a low temp (for me almost always PETG HF) filament in the right that just sits there the entire time. So I would recommend to others having the same issue to try and remove the right nozzle or swap it out for another nozzle you use for high temp when doing high temp prints.
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Any particular brand or model you recommend? Looking on amazon, thereās a hundred different ones, and no obvious way to separate the good from the bad other than reviews (no longer trustworthy on amazon).
Also, the leather gloves donāt mention any particular dwell time rating. Obviously, a high temperature resistance and infinite dwell time would be best, but none that Iāve seen declare a dwell time.
When I zoom in on the photo I took (posted earlier and zoomed in more here):
I would agree with you, but I do see crud on the rectangular piece (is that the temperature sensor?). The only place I donāt see it is in those two little divots. Therefore, I hypothesize that those two divots are where the actual contact is made, and everywhere else is standing off to one degree or another. Does that make sense? On the other hand, the rectangular crud is a different color (a brownish orange), which is different from the black crud. Is it a different color because it didnāt get as hot? Another piece of the puzzle perhaps.
What are those two divots anyway? Are they just for alignment with the the nozzle, or are they like pogo-pin type connectors for passing current or signals? I need an anatomy lesson as to what it is that Iām looking at.
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