Same thing happened to me....control arm worn out on rear suspension.
This is obviously a problem with many discovery sports. I have a 2016.
When your car is on the rack, you can't identify this issue because everything is tight.
Take it off the rack and use a bar to push control arm. If it moves, there's your issue.
This pic is blurry, but you can see where it wears down. Your tire wear will also be affected by this because alignment continues to fail.
Also, there are no after market parts for this particular part. It's genuin parts only..
Hope this helps.
In the pic, where the fingers are is where the Rivet part is worn down. Both areas are shot, so when turning right, the car has zero stability and it feels like you're on ice. 0