I completed quest the killing field, tried several times, always both odiil guys survive, but quest complete message tells me

The Goblins have been defeated; I should return to Valus Odiil and inform him that Antus did not survive.

Thats not true he is alive and can talk with him, then both return to wherever they go.

But i cannot get the reward which i would like.

Any idea. Found not a single mention of this bug anywhere.

I took the mission probably long ago, maybe around level 10 to 20 and i went to do it now as of level 41. Both were waiting where they should and i went with them to the farm then killed the goblins and both survived. Tried many times, even kept throwing healing on antus nonstop, and summoned a storm atronarch to keep the goblins busy, but game still insists antus got killed which is not true.