Edit2: ok I just saw this
Edit: added capx. Bash the ragdoll around to see his head joint become dislodged. Disable the 'on collision' checks to see the difference.
Thanks for taking the time and pointing me to that thread.
I was writing up a response, to say that I think he and I had different issues (my sprites are not stretched, image points seem all ok, etc.) then I thought I'd put together a minimal capx. While I was doing that, I think I found the issue..
When my ragdoll was hitting another physics object, I would change frame of the 'head' object, say from 0 to 1 (it only has three frames). All frames are the same size.
So I would do
->change frame to 1
->wait 1.0 seconds
->change frame to 0
Removing the above for the sample capx seems to keep my ragdoll together. Leaving the Wait on its own is fine (unsurprisingly).
It seems changing frames is enough to screw up the physics processing. Is this reasonable?