** V3 motor has hard CNC7075 material However, it can be used with V1 and V2 motors. The magnets are the same. Only the CNC material is different.
** Motor is just like a car wheel which maintenance (check-up) is required for safety reason. It makes sense because the Car Dealer won't monitor your usage and condition remotely. For motor with Grub Screw, you should check whether both the shaft and grub screw are loose or not. If it is loose, then you should apply some Loctite Glue on it.