Build number: v1.10.0
After confederating Clan Moulder in Mortal Empires, Throt the Unclean still tracks loyalty as if he were a non-unique Skaven Lord. Other Skaven Legendary Lords, such as Queek Headtaker, do not have this issue when confederating their respective factions. This leads to scenarios where Throt the Unclean can defect to form a separatists faction. This was tested as Clan Skryre in Mortal Empires.
-Play a Skaven faction besides Clan Moulder
-Encounter Clan Moulder and build diplomatic relations until confederation is possible
-After confederation with Clan Moulder, recruit Throt the Unclean if he is not currently on the map
I have attached both the manual save of the bug (turn 56) and the auto save prior (turn 55).
This file is attached as well