I don't have that specific model, but I've had luck tightening joints with using tissue paper or clear plastic wrap. For example, if you are able to disassemble and expose the shoulder joint, use a small piece of tissue and insert into the ball socket, then reassemble the ball into the socket and tighten everything up. The tissue takes up any excess space and creates friction to tighten the joint. Has worked for me so hopefully works for you.
I'm having issues taking apart a the leg of this current Ozma model. I'm hoping to tighten up the mechanism that allows the foot to detract and retract. One of them is super loose. Any tips or tricks is appreciated!