Has anyone else had (or read a post about) trouble with the mouthpiece ejecting itself from the unit when heated? If so, please share how it was resolved?
It's getting worse with use. Now, I have to hold it in place with my hands EVERY time I hit on it. The screen in the mouthpiece is not flat and evenly seated anymore. Guess that's due to teflon's expansion/contraction?
Something is wrong, obviously. As others have said this is basically unknown.
Normally you put the top on cold, and it's a fairly tight fit with straight sides. As it heats it should 'lock up', that is the hole gets smaller and the plug gets bigger. You can normally lift a hot HA by the top?
However, PTFE is a very soft plastic. Every time you've forced the hot parts back together you've run the risk of further 'belling' the opening (making it wider at the top than the bottom) and tapering the plug (ending up with it smaller on the bottom than top. Both types of damage will make it worse and degrade. Carefully look at the two surfaces and see if you can detect the tapers. Hopefully it'll be confined to the plug (the hole is backed up by metal), which is easy to replace.
More over, PTFE is 'slick' (low friction) so there's little to hold it against any taper.
If you think the damage is confined to the plug, I'd just contact the maker for another. Sadly, if it's the opening it has to go back. But in either case resist the urge to force it when hot, further damage is sure to result......which fits with the 'getting worse with use' observation.
Nothing but new parts (or serious mechanical work) will make it right.
Screens fit poorly into the plug, they have to or they would pop out again. I dome them upward then flatten them in place. I also use the factory coarse screen to hold a much finer one (3/8 inch?). I also usually throw a loose screen on top of the crucible (5/8 inch? I don't have my HA handy, it's out on loan). This screen is changed out every few loads (I flame them clean when I have a vial full of used ones), this keeps the upper screens much cleaner.
Good luck.
OF