The earlier swing axle in the W110/W111 used a horizontal compensating spring. The later W108 used a hydropneumatic compensating spring to keep the rear level when the trunk was loaded. If car still has its stock hydro spring, it is or has gone bad. There is a replacement spring and bracket available to replace the very expensive stock one.
As for the shifting problem, make sure the shift rod bushings are in good shape. They are still available and easily replaced. See the EPC for your car. You will need the body type, 108.012.
As for the shifting problem, make sure the shift rod bushings are in good shape. They are still available and easily replaced. See the EPC for your car. You will need the body type, 108.012.