Mods Bench says I have some sort of phantom duplicate?

[TruLunaris]

According to my Mods Bench, I have 1 duplicate mod lying around somewhere, but when I sort by Duplicates with the dropdown filter on the right, I'm just shown my mods in alphabetical order, as if I sorted by Name. As far as I understand, this only happens when you try to sort by duplicates when you don't actually have any duplicates. But my mod bench says I do have a duplicate. But sorting by duplicates tells me I don't.

I do have 3 riven mods, but none are for the same weapon.

Imgur link for pictures cuz for some reason imgur doesn't work with the "Insert image from URL thing", even when the link just has one picture >_>
https://imgur.com/y19GpUT