A few weeks ago I had to abandon my much loved blue Dragon after we failed to remove it from a placement. The annoying thing was that this was not at some difficult to access or dangerous spot halfway up a large mountain, but rather at the top of Stanage, at a place where we could sit safely unroped! To add insult to injury we could even get our fingers on and move all the cams of the unit individually! Having never lost a cam to getting it stuck in over 20 years of using them, and having recovered other people's 'jammed' Friends for them, this was upsetting.
What we realised had happened was that the stem of the unit had come unstuck from alloy head of the unit (it looks like it is held in place with epoxy). This wouldn't be dangerous in fall because there is an oversized 'plug' attached to the end of the stem that stops it from pulling through the head of part of the cam BUT when trying to remove the cam you push the stem (and hence the whole cam) in slightly while retracting the individual cams with the trigger. When we were trying to do this the stem was pushing through the head of the Dragon meaning that we couldn't bring the cams in via the trigger. After spending the best part of an hour trying everything we could think of, we both needed to get home so had to leave it. Some one subsequently got it out, so well done them although I imagine if they place it again they will probably face the same issue.
That design of Dragons were recalled shortly after they were released (indeed the cam I lost was a replacement for the original due to that recall) but the recall was not connected to this issue. I sent DMM photos asking whether I could expect the glue to fail on my yellow dragon which is the same design and age. They said the attachment of stem and axle boss is "through interference fit and bonded with glue, meaning it is unlikely for this to happen"*, but of course it did happen with the blue cam!
I've looked carefully at my yellow cam and given it a wiggle and can detect no movement in the stem. Not really sure what to suggest to other Dragon users besides keep an eye on your cams and if you see the glue has failed maybe don't place that cam as there seems to be a good chance it will be very difficult to get out again. I would be very interested to hear if anyone else has had this happen to their Dragons though. Mine were from 2010:
https://www.ukclimbing.com/gear/review.php?id=3213 and have been regularly used since then so I fully accept they have seen plenty of wear and tear.
*I should add to be fair that DMM felt from the photos the cam was stuck due to being over-cammed. I would accept that it was in a tight placement at the bottom of its expansion range, but it was not over-cammed in that all the four cams could be manipulated manually. I feel if the stem hadn't been loose it would have come out without much drama.