For your 48-inch slow-rise roller shade that does not retract, the most common cause is a worn or broken internal spring. Replacing the medium tension spring typically restores proper retraction. The slow-rise auto stop is a separate component that controls the shade’s stopping position during retraction and usually only needs replacement if the shade retracts but stops incorrectly or moves unevenly. For the second shade that does not stay down and rolls back up, this is typically an issue with the slow-rise auto stop mechanism rather than the spring. To select the correct replacement spring, knowing the roller tube diameter (usually 1" or 1.25") helps; you may also send a photo of the shade tube for assistance. Replacement parts for both the medium spring and slow-rise auto stop are available for purchase to resolve these issues.