When I got it, my SP-15 had springs attached to the rear roller(photo attached). I’ve noticed that the tension causes the roller height to decrease rather than helping to hold it steady. There’s no spring shown in the manual & it looks like someone long ago added a bolt that would anchor the end of the spring. Is this a practice that others have noticed? Was it considered a ‘fix’ for the tendency of the roller height to get out of adjustment? I’ve had the springs off for a few weeks now, and it seems better without them.