Another simple solution is to stress the spring dowel joints with friction and heat. Just get any metal rod like a tiny screwdriver for mobile phone repair. Preferably those that taper out, then just do a dozen or so quick turns with a little inward push. This should expand the spring dowel joints. Let cool and see if the joint tightened.
I honestly just got into collecting Bandai DX stuff. Don't know if this has been posted but here's my solution for flimsy YF-29 wing swivels, ver. 1.