You might want to check the USB -B connector port. If it doesn't look like this one, you might want to go back for warranty, or you'd might want to consider a ninja mod.
Here's how the orange bugger should look:
Here's what could be the cause:
Just make sure the metal pins don't connect when wanting to use the s4.
I have done this by cutting up some cardboard just that I am able to plug and unplug the S4. Will try to take some pics later on.
Just make sure the cardboard isn't too wide that you are no longer able to connect the USB cable.
Here's what it looks like after ninja modding it:
In case of warranty, excellent! This ofcourse is the best way.
In case of high need go for teh ninja skillz mod.
In case of wanting a structural solution, replace the entire USB B connector port.