I'm assuming its a desync issue; I've noticed it not just with chests but certain items (like Briars) as well, sometimes I'm far away and still get hit, others I'm just on the edge of the item's aoe and I don't get hit by it. I've also managed to heavy/bachuss someone once or twice just after I pass them.

The amount of times I've absolutely needed a chest and just clipped through it though...
The rage was unreal.