I bought my Plaubel Makina 67W from Frank Marshman, who used to run the repair shop "Camera Wiz" and now does repairs from his home. He's an expert with Plaubels, and he told me that I should set the focus to infinity when collapsing the lens, and not to let it bang out or bang back in -- gently put it in and out with your hand. So far I've had no issues with mine.