Uploading mission to SITL

Hello, i am trying to upload a set of waypoints to the sitl copter, but i am facing this issue where whenever i have sent my final waypoint in a MISSION_ITEM message, the sitl copter does seem to recognise that it is the last waypoint and responds with MISSION_ACK message, however, more often than not, the value of the MISSION_ACK message type field (the results) does not correspond to any of the values in the MAV_MISSION_RESULT enum. Also, the type field value appears to be erratic.

When i then try to re-read the waypoints of the sitl copter using mission planner, it does show that my waypoints have been uploaded successfully.

May i know if anyone here has any advice for this? Thanks!