Commands are only working in a certain area

When I do a these two commands:

  /tp @e[type=Silverfish,name=Hitblock] @p

&

  /tp @e[type=Silverfish,name=Hitblock] ~ ~-5 ~

it makes the Silverfish apear -5 blocks bellow me, which is what I want, but when I move these commands to a different area (These commands are in a commandblock which is hooked up to a clock) and put the same command in the command block, it only activates the one command which is:

  /tp @e[type=Silverfish,name=Hitblock] @p

and doesn't make the silverfish appear underneath me. I am not sure why this is happening and I am playing on a flatland world so the Ground is only four blocks thick, but i don't think it is that because it should work when i fly up. The command I am using to summon the Silverfish is this:

 /summon Silverfish ~ ~ ~-2 {CustomName:Hitblock,Attributes:[{Name:generic.movementSpeed,Base:0.001}]} 

I attached a video file to show you clearly whats going on