Question Editor Asset Stealing

In Unity 5.X.X I've always had the issue of the editor stealing assets and was wondering if someone could shed some light on this. Is it a bug, is it a feature...WHAT THE HELL!?

So if you're wondering what the hell does he mean "asset stealing" I mean if you have a model in your assets, say a 55 gallon drum. You want to place a few on your scene. You drag one on fine...then you drag the next and the first one is stolen, popping up at the edge of the scene from where you dragged it. This doesn't happen 100% of the time but it's beyond obnoxious and makes doing anything a nightmare. When it steals an object you can't undo it. You're only recourse is to save before you drag something...if it steals it...close without saving and reopen...what a massive time waste and PITA.

I've tried all sorts of things to fix this thinking maybe it was an issue when dragging across the inspector or hierarchy panels. Outside save/restart the worst "workaround" is drag to the hierarchy panel and release then copy paste XYZ coords from something else near where you want it. Paste said coords in and then fine tune, again what a nightmare!