You might need new RTABs or Rear Trailing Arm Bushings. How old are they?
I recntly replaced mine after 57K and the rear feels more stable and less knocking around during manuevering or ridng over bumps.
All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident. - Arthur Schopenhauer