I’ve had the same waist flopping behavior. Wrap one hand around her hips, the other around her shoulders. Pull her firmly apart at the waist, don’t yank. Then let her slowly come back together. That sometimes straightens out the elastic and she is more upright. Same with a wayward “kicky” leg, pull it firmly out and then back into place. I’m sorry I don’t have a direct YouTube link, search Jamieshow on YouTube and a number of repair and general tip videos come up.