v8.8.1 - Classic Era
More specifically this quest in the questline:
https://www.wowhead.com/classic/quest=67/the-legend-of-stalvan

It shows in the tracker as complete, even though it is not.
It is not complete in the Blizzard quest log either.
Same issue with the next quest in the questline.

This is how Questie deals with quests without objectives. They are labeled as complete, because... they are.
This is not a bug if you ask me, it's just how it is with Questie. (personally i'd also want to see it exactly how it is now, showing complete for quests without objectives).

No, the chest is actually the quest finisher.

Then this seems to be one of these quests without a real objective, but still has one.

So you interact with the chest and then the quest will be complete and you can turn it back in at the NPC that you got the quest from, right @Painstormx ?

Well, I have to disagree that they are complete. If it was complete, I would be able to turn it in and that is not the case.
For this quest, I actually have to go to Moonbrook Schoolhouse to open a box and that is when it completes. That is also when Blizzards quest log sees it as complete and you can turn it in.
But I know Questie is currently having some general issues identifying completion of quests without quest objectives, so it might be that general issue.

If the chest is actually both the hidden objective and the finisher, then @Cabro is correct and Questie is handling it fine.
I just checked a char on this quest and Questie does show a yellow '?' in the Moonbrook Schoolhouse.