Tested only in spiritualists and martial artists.
You can not pick up the loot thrown by the monsters you kill at maximum distance.
How to reproduce it.
Being a spiritualist, select a monster and eliminate it from the maximum attack range (quickly). Without moving from your place, right click on any of the objects that fell. It will not allow you to grab them until you move (either with left click or WASD).
Note: if the monster reaches its own attack range before you kill him, the bug does not happen.
Martial artists do not have this problem, I guess it will be associated only with range classes, and the time of the monster's doing the chase.