This mission seems to never register it was completed.

I'll kill 25%+ of the Dimok craft, and I'll even wait for also of Asbo to be captured and hyperspace away... all goals green.

When I leave battle, it treats it as a failed mission.

In the meantime, I'll go other battles. I just like going through the Harkov missions first to get rid of the traitor sooner.

What goal does it say was failed?

It says the Protector must survive until all missions completed. It's still alive.

I tried copying the 94 mission (I backed the 98 mission up) as it doesn't have that requirement, and even though all primary are completed, it still says I failed.