What gameplay feature is this bug affecting?
Sub Male Slots

What's the issue? Please include any error messages you receive and as much detail as possible.
I just early retired my king so I could have space for an adolescent male to age up and it's saying I have 3/3 slots taken but I only have two sub males. I tried everything to fix it except getting rid of my sub males and he ages up next rollover.

Any links relating to this bug? For example, if a particular lion is bugging, what is the link to that lion?
https://www.lioden.com/lion.php?mid=32922 I can't link directly to the pride but this is the main I just replaced my old one with.

Any screenshots you can provide us with?
https://prnt.sc/wa4t4j

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:
I don't know how it happened, this is my first time retiring a main male.