/fill command on glass pane doesn't connect to the sides.

I was making a house and used the /fill connand to fill in glass panes, but the edges wouldnt connect.

What I expected to happen was the glass panes to fill in normaly

What happend was the edges wouldnt connect

Steps to reproduce:

1. Go to a corner of the area you want to fill

2. Remember co-ordinates.  (idk how to explain)

3. Go to other corner and type in:                                                                                                                                                                                                    /fill "previous co-ordinates" "current co-ordnates" minecraft:glass_pane

4. Notice that it doesnt fill in the sides