If I were to guess, I would wager you have some form of levitate on. If not, it is probably just because of the size of the npc box. Here's what typically happens in macros that use /moveto: Your ArrivalDist or /stick mdist command has you levitating farther from the object than the Distance3D check required/used by some other mechanism, such as /loot.
Default ArrivalDist is 8, which, if levating.. may be too high or plenty low enough.
Mq2moveUtils.Ini:
[MoveTo]
ArrivalDist=8.00
You can play with that. Lower tries to get you closer, but may conflict with levitate. Higher makes you jiggle less, but might be too far to loot. I think you can actually loot from ~20' Distance3D. But the key is 3D not Distance (which is what ArrivalDist checks)