Low Unlootable drop

Honestly, this one happens just about anywhere you kill mobs pushed to the border of the map, usually not as visual as in here as the map borders stop here before the visual ends.
This is most easy to notice when using pets with meso/item loot, once an item is beyond the looting border, the pet will just hug this 'wall' and ignores anything else that doesn't land on top of it because it's set to loot in order of drops.
Easy way to reproduce this is using PickPocket on a shadower and notice all the meso bundles that are unlootable because they are out of map bounds, other ways are like I said, push mobs to the map border and see drops become unavailable.

 

Legends has made some efforts to deter this and it does happen less often now.

I somewhat recall that in GMS when this would happen, the item would automatically rebound and fall well within the bounds of the map. The rebound would be quite large though and end up far away from the other dropped items that didn't fall out of bounds.

 

What item is that? We can refund you it. Looks like gacha or nx?

 

looks like a rare gach

however if you leave the map and come back, it should solve the loot issues