After identifying the Monolith carrying Lumber, if you go straight to the destination you can't complete the mission. The cargo pods spawn moving at 400 speed, making them very hard to tractor, and even if you do successfully and destroy everything else, the mission doesn't complete. Instead, land somewhere after identifying the Monolith and you'll get the email for the third part of the mission, skipping the second part. Now the cargo pods will be moving at 200, there will be no Lasertowers and four Skulls will shortly appear. Also, there will be four Military Lights "Enviro Suits", which is another glitch. However, the mission can be beaten and will give 13,500 instead of 2,700 Credits.
If the mission glitches out and doesn't complete, it doesn't fail either. You're stuck with it until it fails automatically after several landings.
The Tri-System Hunters mission never fails after landing several times, but it won't activate upon arriving at Janus IV either. So it'll be stuck in your Diary blocking a slot permanently. This can only be avoided by going there fairly quickly, within a few landings.