I played 5 different new games on 0.5.21.1 before switching back to the stable 0.5.21. On all 5 games, the missions for the harvester and guard did not appear. They weren't in the mission log and i wasn't prompted for them. I totally forgot about these missions until I switched back to the stable branch and started a new game, at which point they showed up. Can't say I actually MISS those missions, but seems like they were either removed or the trigger isn't working.