Problem with Kudos / Thumbs Up !

Just a heads up:
I have seen kudos go down when clicked.
The number actually went down after clicking it.

Let me explain further:
I have been re-reading a few I stories liked. And have been clicking the new thumbs up button on them not being sure if i had kudoed them before. A couple of times now I have seen the number go down when I do so.

More background (not entirely relevant to the problem) :
When I first I did not always Kudo stuff when I first found this site, at first I was not registered & then I wasn't sure what exactly kudos meant, that is what standard to apply. I have since decided how ever other may use them I will give one for any story I enjoy regardless of what standards others apply. Also at times in the past I could not tell if a kudo registered, I do know at lest a few failed because the site wen down while i was reading. I therefore have been clicking them when re-reading stories I liked. I assumed it was safe and would not add an extra one of I already kudoed it, but would add it if i somehow missed it.

Continued detailed explanation:
Most of the time I see no change in number I probably already kudoed that one in the past, a few I have seen go up. But I then thought I saw one go down. I have since been watching it carefully when I do so and just saw another on go down instead of up.* Clicking it again after that seemed to do nothing one way or the other.

I am now not sure if I should or should not click them if I'm not sure if I clicked it or got one to register in the past.

Should I continue to click them or not?

~Hypatia >i<

* The one I am sure of was ("Masks" Chapter 13 by Bailey Summers).