What gameplay feature is this bug affecting?
Breeding

What's the issue? Please include any error messages you receive and as much detail as possible.
Several days ago (I believe it was Saturday) I got a Stud request, but the notification was broken (it showed as "Game Notification", not a request from specific user, I also have a screenshot that I didn't get other request from that user). Since I have already had 0/15 breeding slots available, I decided to wait till Monday to breed the girl (sometimes people send requests for future).
But when I tried to breed that girl today (on Monday), I got an error that she has been already bred. I checked her and found that she was bred a day before (while I didn't have slots) by owner itself, and has 2 days before birth. I rejected that request.
But I realized that there was a bug only when that user messaged me displeased PM and blocked me, so that means other player also didn't realized that they aready bred that girl. That's why I don't have a screenshot showing me message that "lioness cannot be bred so soon" on studding page.

Any links relating to this bug? For example, if a particular lion is bugging, what is the link to that lion?
lion: https://www.lioden.com/lion.php?id=794137780520
stud request (link for mods): https://www.lioden.com/readmsg.php?id=892685955645
rejection of stud request: https://www.lioden.com/readmsg.php?id=892686042908

Any screenshots you can provide us with?
https://imgur.com/a/onT2dYv

Please provide us with step by step explanation how this bug happened so we can attempt to replicate it. If it's complex, please include screenshots where possible:
Not sure that i's my fault. I already got broken request