I submitted this one today as well, as ticket #1,181,929.
I was using Beam Fire at Will while engaging the Kang so that I could hit the asteroid and the Klingon ship at the same time. Since "destroy the asteroid" was one of the listed objectives while I was engaging the Kang, and since the Kang had been firing at the asteroid before I attacked the enemy ship, I didn't expect there to be an issue.
Edited to add: A few minutes ago I returned to the system to attempt resuming the mission again. This time I was returned to the beginning of the final space portion (i.e., destroy the escorts) and was able to complete the mission normally.