I took my very first wooden A9 that I made in Dec. 2015 and got it working like new again. This video shows how.
The new versions of A9 don’t ever get this loose, however as they use different materials that hold their tensile strength whereas the wood on wood combo had the tendency of losing strength even when it wasn’t being used. (wood just permanently takes the extended shape after a period of time).
This could also be a great way to prepare a doll for stop-motion animation. Might even help you fix up some other dolls you have that have gotten loose over the years.
I hope it’ helps regardless of the manikin you use 🙂