Guild Wars 2

I don’t frequent the forum so I apologize if this is common knowledge, but my Google search and forum search produced no results.

My guild completed “Save Our Supplies”, a guild challenge in Iron Marches, for the second time in a row without actually doing anything. The first time, after we started the challenge in the Guild Panel and wp’d to the location, there was a guild already doing it. A few members went ahead and started helping them. The person in our guild who knows most about these events and usually leads them said that those persons would need to exit the map or the event will complete and we won’t be able to do it. We thought they all did, but that happened anyway.

The second time only a few of us entered the map to keep an eye on the timer of the guild currently doing it before we’d invite the rest in. None of us participated in any way or even went close enough to be able to see the other guild’s tags, but again the challenge completed as the other guild finished.

What’s going on? What are we messing up? The only thing I can think of is that I stepped inside the orange circle that appears on the minimap when you get in the challenge’s range, but you can’t see the timer without stepping inside it. Surely this is not enough to complete it?`

Thank you for your time.