Can I ask anyone is this a concern for something to break? I had my car in to service 9 days ago for this exact issue. They said the car was out of alignment (literally the ONE driver rear tire only) they fixed the alignment and everything was fine. Until today. Now it’s swaying out the back end so badly it gives me vertigo when driving. my rear drive unit is due to be replaced as they have the parts “on order” so I really don’t want to pay them for labor to do all this crap when I know they’ll get my DU and have to drop it anyhow. No one is able to tell me if it’s ok for me to drive the car until the DU arrives.
Do you have a jack at home? Lift each corner off the ground and see if there's any any slack in the wheel that would indicate a bushing is worn (put your hands at 3 and 9 o-clock and wiggle, same at 12 and 6.)