One of the notifications I got was about the need to take care of the rival and it tried to display their power and vulnerability, however the vulnerability came out a little... let's say distorted...

It ended up like that in the main message as well as in one of the tooltips (as can be seen in the attached screenshot)

I know that the vulnerability was at 0% at that moment

Something to consider as well is that i'm playing on linux (arch linux, 100% up to date, should lib versions be needed tell me)

That's really weird: I'm using the same system to display their vulnerability as I do to display their power, so if one worked then the other should as well. I'll take a look for the next build and see what's going on.