Found a bug with the first forest mission off the ice world, appears to be called Last Man Standing. One of the enemies is in the middle of a hill or doesn't register as destroyed so the mission won't end.

I've seen enemies stuck in terrain a couple times before - though never with a mission objective target (on multiple different biomes). Sometimes it's possible to find an angle where you can actually shoot them, but otherwise it may be necessary to reload the mission (or even go back farther). Still, if you have to reload you shouldn't lose much progress at least - the game autosaves very frequently, with saves on system arrival, mission start, and mission completion - and at least in the same system things don't get rerolled.

Thanks for the response.
I restarted the mission and it didn't happen the second time.