Whenever a guild quest gets an update to show something was killed/gathered it causes the UI location to reset to the start position. If in inventory it goes to the top left, start menu it goes top left, trying to view/scroll they quests it goes to the top, trying to accept a quest from an NPC with multiple quests, trying to view guild members.

I don't think this is the only thing that causes the UI to reset like described but it is one of the most notable especially in kill quests with multiple people helping.