I think I have managed to identify an issue with the King's Tomb dungeon/instance, whenever the player wizard loses a fight or teleports out, the dungeon/instance resets regardless of how much time has passed.
According to this older thread: https://www.wizard101.com/forum/zafaria/what-happened-50350; the issue was the system sometimes switching the wizard's realm, but is now doing this regardless of whether this happens or not. In addition, marking a spot in the dungeon/instance no longer works and gives the reset pop-up instead.
Note: I am not sure if the King's Tomb is a dungeon or instance, it has the instance timer of 5 min(that does not work and resets the place regardless), but is referred to as a dungeon by the pop-up when marking a location. In addition, after being out of the dungeon, the quest arrow freezes in place(though it still tracks distance correctly).
I didn't have any actual issues completing the dungeon with another wizard, but I would like to point out this bug to prevent further issues with other wizards.
