I had the same problem. I couldn't summon support on the stairs. This led to me having to drop and restart the mission twice before I successfully completed it. Once because trying to draw off and attack the Romulans solo ended in them camping all over my respawn point (leading to me dying over, and over, and over, and…
I was thinking and "Unimatrix Zero" does leave open the question of what happened to the Borg freed in that episode. We know at least some of them (like Korok) were able to seize control of the vessels they were on. Revisiting them could open up the possibility of a playable Borg faction separate from the NPC enemies…