I had a quest for looting a foot slot item. I collected many foot slot items while the quest was active (yes, it was blue) but the quest wasn't going away. After a few hours, I collect a rare item from the Thumper (rare bunny). The quest then goes away and a new one comes up.
Another problem related to this: A user had a quest for fishing. After doing an estuary, the quest changed to loot a rare item.