After several hours of inactivity of a master alt, while extensive use on a slave alt, the master alt gets moved into the void and is unable to select unless one reloads/logs on and off from the entire site.
On several occasions where I have been online, rp'ing on a slave alt that is connected to my master alt and after a few hours (sometimes minutes), without interacting or posting on master alt in main chat, the master disappears from the profiles list entirely. It still appears within the 'My Alts' list with proper master and slave labels. Only way to solve the issue is by reloading the entire site.
Will update thread with picture, once it happens again.