Guild Wars 2

I have just swept around Queensdale and done the events associated with the hot air balloons, both escort and attacks. However, I looted the first chest on the first tower, but when I visited the second tower, the chest was already open and unable to be looted.

Is looting these chests a once a day feature? Once per zone? Tied to account? Tied to character? Or bugged?

Update: Queensdale towers seemw to be bugged. I was able to loot both towers in Wayfarer foothills.

It doesn’t count the second tower for the achievement either. Other areas have worked fine so far, just Queensdale with this problem.