One camera short of a lens!!!

I now know why my shots I have been taking, are not as sharp as I would like them to be. Well this is the reason why,
Back in June last year I invested in a Sigma 18-250 lens. To begin with the shots were pin sharp, great I thought, but as time has passed the images have not been coming up as sharp as I like. 
I have tried everything and all of your suggestions but to no avail, so I took it back to the camera shop I bought it from.

They tested it on a like for like camera, same results blurred, then they tried it on the model above K-3 still the same and whilst it was on the camera it was 'hunting' to focus.. 
The lens has now been returned for repair which will be about 4-6 weeks and on its return I will be all sharp again. Hey ho I suppose a duff one slips through the net sometimes. 
What this will do is make me use the other lenses I have which I will admit I do not use as much as I could.!!
I have always enjoyed the service I have had from the camera shop where I have bought all my kit and they know what they are talking about. Sorry cannot advertise them here.!!

Hope you are all well.
Take care.