Was running some Litchi missions and while landing on the second mission the P4P began spinning/undulating and crashed into grass about 25' (7.5 meters) from the launch site. Physical damage seemed to be limited to landing gear/antennas. Would have probably been much worse if crash was at landing site (which was concrete). Sent to DJI for repairs. Prop came off in flight and was able to recover the prop with the mounting plate still inside. Appears the three screws either stripped or backed out due to vibration. It was my second flight of the day (about 6 minutes) and part of my preflight routine is to "jiggle" the props to insure they are tight; they were. Wondering if anyone else has had this problem.