I experienced both this issue and a different one while trying to complete this mission today. I'm about to reset it for a second time (take three!) to see if I can't get it to work this time.
The first time I had this issue, and the second time I couldn't get the last group to appear. I think it's because I was assaulted at the door before finishing the dialogue, so the first group wasn't credited.
Edit: to clarify, the first time I went in the guy that alerts the troops didn't spawn and so a few of the force fields just led to dead ends (which confused me as I was prompted to take out groups but didn't get credit for any of them, so I figured I had to go into the fielded areas). The second time one of my officers spawned inside of the cave wall and glitched the group in the big room to the right of the entrance to attack before I had been alerted that Cardassians were there to be cleared out and so I never got credit for it.
[Silently he unholsters the [Zombie Control Sniper Rifle of Epicosity Mk XIV], shoots and vaporizes this Zombie thread!]
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