Maybe a rear lower control arm is collapsing? It does happen, especially if the car is rusty. Rear wheel top will be pointing inward.

Could also be a broken spring, either front or rear. I know you put in new rear springs, but you may need to check them again...

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC