While doing quests I noticed a pretty glaring bug. I thought it was just me the first couple of times but it's pretty consistent. If the screen that tells you "You do not have an active quest" comes up, it still uses up one of your quest turns. I try to hit 25 per day on the quests I do, but I run out of turns early sometimes (I definitely am not failing quests when this happens) and this is consistently the cause.
Getting told we don't have a quest shouldn't waste a quest turn. The easiest way to make this happen (for testing) is just by double-clicking the "Hand in items" button on the quest. I think it's happened for other reasons as well, anything from refreshing the quest rewards page accidentally to Res lagging really hard while it was loading and then seemingly just giving up? These aren't as consistent for testing though and most often it comes from clicking a second time during lag because I think I missed the button the first time.