i had this problem yesterday twice but the second time i was with a friend and we decided to kill everything else after running away, because the zombie one didn't deagro, i realized his disruptor beams didn't leave they were a graphical glitch but useful they started to come from a new location turns out he respawned and we killed him and completed after a few deaths because of big *** torpedoes
I'm no longer getting an unkillable Teneb, but I have still been unable to complete this mission twice now, today. It simply goes thru the entire mission 'script' then when I get back out to Sector Space, I haven't received credit and have to repeat it from the "Den of Thieves" step.
I'm also getting to the point where I've gone through the whole mission, got the Romulan to warp out, beamed to space and dealt with his ship/waves and it is still unupdated at Under the Cover of Night - Den of Thieves - Go To Agrama Prime.
Dropped the mission and redid the whole thing only to be left with the same scenario.
Okay, I've been away far too long from STO, but where is the Agrama Solar System? I tried to look through my loggs and an unable to locate this system. The last time I played this mission, I kept on getting killed by everyone while trying to scan the cargo ships and I gave up after that point.