Exact same thing as @DeusDarken describes happened to both me and my girlfriend over the weekend. It's actually even slightly weirder than that for us, though.
In my case, I had JUST completed the mission when this happened. I received the reward but the mission progress reset to 0 for all 3 categories. However, I do not make any progress toward them when playing -- they are stuck at 0. Not a big deal for me, since as I said, I already got the reward.
For my girlfriend, it's more of a problem, because she had completed 2 of the 3 categories, and was almost done with the 3rd when this happened. Like me, all 3 of hers reset to 0 progress. Unlike me, it does allow her to progress on one of them -- the one she had not previously completed. But she doesn't want to go through the effort of doing it again, since it required her to adopt a playstyle that she doesn't especially enjoy. And there's no guarantee that it would even give her the reward if she did finish that one category, since the game seems to think she has made no progress toward the other 2 categories.
I cannot prove it, but I think more than just my mission progress got reset when this happened. I was looking at one of the locked items and it required a number of frag grenade kills. It showed that I had only a single frag grenade kill so far, but I have definitely killed more than that since I started playing 2042. I don't know for sure that this got reset at the same time as the rest of this, but it made me wonder.
