title_body: Proper rotor fastening (Nyloc nut)
upvoted_answer: I've had the same thing happen when using these same motors and props (and others). The propeller seems to get stuck at a point where it is not flush with the motor. From my experience, the solution is as simple as tightening it further. I use a tool like this that allows me to apply more force than a typical prop-tightening tool.
  It should look like this when fastened correctly, with the prop sitting flush with both the motor bell and the nut: