Guild Wars 2

I am searching the items for the Precursor (level1) of the Predator. And i can not menage to find some items.
For example “Asuran Experimental Weapon” or “Scarlet’s Prototype Mechanism”

In this both cases i am pretty shure that i was standing in front of them without beeng able to to collect them.
(Scarlet’s Laboratory is not that big that somebody can miss that item)

Is there a bug or unfinished design that makes it impossible to collect?

*PS: Plz dont spoiler the position of the items, i want to find them myself

Numerous collections are bugged, Twilight, Sunrise, Bolt, to name a few. It’s really frustrating as this is one of the main features I was looking forward to most.