On the other Hyper forum someone reported that some Loctite can erode plastic. Just reporting, have no idea is true.I guess you mean the heads, rather than the stems? I have one that often shifts but haven't worked out any way to tighten it. My only thought is to try and infuse some Loctite 601 into the ball-joint but I doubt it would last even if it worked.
Keep us posted...I'll have to try a drop of Loctite on the plastic and see. Only problem with teflon tape is I assume you'd need to actually get it into the ball-joint. Just winding it around the outside wouldn't help much if at all, though if some jammed into the gap it might work.