Guild Wars 2

Having found impossible to complete alone I took a friend along on my personal story- we did the objectives but instance failed to complete. Is this bugged or were we just unlucky?

We completed all listed objectives, starting with talking to Thurkill, using the cannon to blast open the doors to the mine, killed the mobs, then entered the mine and destroyed the weapon prototype. The objectives were ticked up as completed. There were a couple of the archers with Thurkill who were stationary and firing at nothing and although Thurkill himself was still moving with me I could not speak with him

I see that someone else is experiencing this problem so further feedback appreciated

Thank you very much