I'm getting this too and It's been going on for several days now. For me it's the "I give up"-emote that is "awarded".
I've noticed that I get one prompt (or pop-up window) per every instance of specific events. There might be other factors that I'm forgetting here, but these are the ones I've noticed:
- Every new star card acquired (either from crate or through upgrade via crafting)
- Each time I exit to the main menu
- Every new emote or victory pose acquired, regardless of class/character
So, not it's not obvious I suppose, but it looks to me that the problem lies with the pop-up function getting stuck on a specific acquisition at some point, without being able to scrap the old data. I'm not a programmer, but maybe the algorithm that tracks which items are unlocked and which aren't has a certain limit to how much it can process? I remember I had troubles with this during the beta as well, with items showing up as "new" no matter what I did (though, without an error code attached to it).
Hope this info helps in figuring something out. I'm on Xbox btw.