Data page WP drop-down is not populated first time, only ever reaches about 96 waypoints

If I have a large mission loaded, the very first time I open the drop-down it only shows "0: Home" and "1:xxx". I have to open it a second time to see the populated list.


Also today when I tried to use it in the field, it only shows 96 waypoints where there were actually over 120. This was quite annoying because I really wanted to jump the vehicle to the end of the mission where I had some waypoints to get it home. Because I couldn't figure out how to skip forward in the waypoints I had to uses Guided and manually put in the points one by one. Sadly when I try to recreate the issue now using SITL I can't reproduce it but it certainly wasn't my imagination.

Start in the Mission Planner Data page and reproduce the report with a large mission: compare the first and second openings of the waypoint drop-down, then check a mission with more than 96 waypoints. Done means the list is populated on the first opening and exposes all mission waypoints; SITL may not reproduce the field issue.

Written by the indexing model from the issue text.