oh the poor little thing. something is definitely not right and it is weird that it just started happening after the microchip was implanted. It is possible that something happened when he did the injection or it may not be related at all. a full cbc/chem panel should be done tomorrow as well as an x-ray of the thorax to start with. You may then need to be referred to an internal med specialist or a neurologist.
the "hub" is part of the syringe and needle. its that little space in between the actual needle and the measureable part of the syringe.
here are some pictures:
http://image.made-in-china.com/2f0j0...le-Needles.jpg http://www.influvac.co.uk/images/syringe.gif
so by saying it was off he might have meant that the needle wasn't screwed on properly and he just had to tighten it. that happens with syringes that comes with needles, sometimes they are just not securely tightened so you always need to check that.