I think I found a possibly related problem with surrender.
If the enemies surrender, you don't get "unlockedResearch" reward (the mission doesn't count as success from that perspective?).
I noticed this on an XCF mission that is supposed to run only once (if successfully completed): I got the second time. Looking at the save I didn't get the "unlockedResearch" reward the first time I played this.
Unfortunately I no longer recall whether I played the first time with this fix included or not. I suppose I can try see if this issue occurs again by doing the mission again and trying to get the success by enemies surrendering.
I write this on this thread at least tentatively until I can confirm whether this qualifies as a new bug or not.