In free movement, from what I remember I tested, the interactable object needs to be present in the middle third of the player character doing the interaction.
So if your player model is six voxel high, it doesn't register an interactable object in front of it, if it is 2 voxels or lower, or 4 voxels and higher. Not sure why, just know it does. Probably a thing that will be changed at some point.