For some reason, in the command block interface, when I type the /fill command, after the last coordinate is placed, I click the [space] bar, instead of adding a [space], it closes my Minecraft tab out.

So, if you have a command block that you want to set the command to "/fill 54 78 -30 75 90 -32 bricks," the [space] between "bricks" and "-32" is the way you exit Minecraft.   I don't have an attachment because I don't take video nor photos. Sorry.