Guild Wars 2

I noticed that in the adventure Scrap Rifle Field Test some chaks in some runs didn’t respawn leading to the impossibility to achieve gold reward.
From what i experienced this seems to happen when you die, reset the adventure and pressing play before the enemies counter and the timer of the previous run is still on the screen. (After pressing reset the enemies counter and the timer of the just failed run remain on the screen for a few seconds)
Waiting for a few seconds to make the timer disappear before pressing play seems to prevent the bug.

For people who are terrible at this mini game (e.g. me), it also makes it hard to get bronze. Are there supposed to be any foes at Scrap Rifle or Shooting Gallery?