WowAce

Add-on version Rarity-r695
I updated the add-on a few days ago and have exited/relogged multiple times during that time-frame.
I've attacked, killed and looted the Sha of Anger once this week, but have noticed upon consecutive kills on the same toon, that Rarity counts the new kills as a 'loot chance' and increases my percentage to get the Heavenly Onyx Cloud Serpent accordingly. Of course, seeing as how I can only technically loot the mount once a week, I believe this to be a bug.

This is a limitation of relying on Blizzard's API. Whenever you kill Sha of Anger, your statistic (https://www.wowhead.com/achievement=6989/sha-of-anger-kills-kun-lai-summit) increases and so does the attempt counter in Rarity.

Theoretically, the addon could check if you completed the loot lockout quest, but then there's the issue of the bonus roll still being able to award the mount. It might be possible to solve this problem, too, but in all honesty... I don't think it's worth my very limited time to add this, considering most people probably don't kill the boss more than once per week anyway. I mean, why would they if it doesn't give any loot?

If you really think it's important I can add an issue for it on GitHub, but seeing how there are like 100 others still open I doubt it'd be resolved anytime soon :/ That's unfortunate, but just the reality with no one else doing any work on the addon after Allara left.

Update: OK,  here's the status (https://github.com/SacredDuckwhale/Rarity/issues/161). We'll see how soon I can get to it...

I only happened to notice it after relogging on my main and just killing the Sha for fun, since it was up as soon as I logged back in. I thought I may have noticed it wrong, so I waited for the Sha to respawn and killed it again, watching the loot percentage, just in case. Just thought maybe I'd point it out, in case it might effect some other intricate counter.