I have both mechanical and archeology field skills to level 4. However, my mission console does not have the required "off the record" mission to get them to level 5. Anyone know if something else is required?
The "Off the Record" mission only requires a level 4 Field Skill and nothing else. The reason you can't find them, is because of how the BLADE terminal works.
The terminal only has a limited space for missions, and therefore cannot display all missions at once. Because of that, missions will be displayed at random. Once they appear on the terminal, you should immediately accept them before exiting. If you don't, another mission may take its place. When this happens, you may need to visit the BLADE terminal several times before the mission appears again.
These missions are random and semi-rare. You may need to exit and open the terminal multiple times before it will appear. All of them appeared near the top of the list for me.