I have a character that is several planets ahead of my friend I am playing with in split-screen co-op.
When I finished my session with him, twice now, I am unable to fast travel to plants that my character has been to (and has quests for) that we did not reach in our session together.
For instance, I had played with him after I had gone to Promethea solo, we did not make it off of Pandora; when I started my solo campaign I was on Sanctuary and could see Promethea in Orbit view, but could not select it to fast travel. So now I cannot play this character until I join a session that has caught up to my acquired planets.
This has happened again on another planet, making it a repeatable bug.