I've read on multiple reviews of one of my missions that the mobs respawn themselves repeatedly on both the space and ground maps, making wandering around a bit frustrating. I did not set them up to do so, nor did I even know that option existed.

Maybe it's just my lack of knowledge on some of this. Is this even possible or is it just a bug? And if so on either, how does one fix it?

A group will respawn if you leave the group long enough

I thought that was the case as well, but I recently published a second mission that does the same thing. It's not "after a while". They all respawn within 10 seconds of being defeated, making the mission far more difficult than necessary.

Edit: This is from the mission:
Dark Alliance Part 1 (ST-HPVNOTTZY)

I'll look into this.

Just a theory, since this is happening in both missions I created (ST-HPVNOTTZY and ST-HBGN68GTL).

There are times when I double click the NPC Groups on the map to change the type of enemy that is encountered (from Hirogen, to Cardassian, etc.), or copy them to other areas of the map. Could there be traces of the older unit left behind? It's just a theory. Trying to connect what I do in both missions that would make this happen....