Good diagnosis and fix, however in the long term DJI has come out with an engineering revision for Phantom 4 series prop hubs. The new hubs do not use a "leaf spring" like the originals did. The concern was that the leaf springs would fail from metal fatigue at the radius right near the top of the motor housing after frequent use. The new ones do away with the leaf springs and replace it with a central coil spring. The original ones may not have even been an issue if the props are not frequently put on and off, but some do, thus the engineering change. The new hubs from DJI run about 10.00 US total (get two sets, as each one contains one "dotted" and one "non-dotted", so you'll need two pairs.