play between lens and camera

Hi all,
I have noticed recently that when my newly repaired sigma 150-500mm is attached to my K7 there is a little ''play''between them
Its only miniscule probably a mm or less - but sometimes I lose AF etc for a few brief seconds...which can be a pain...
I was trying to think of ways to remedy this issue without sending that Lens away for repair again..
I have been thinking of attaching a few very thin sheets of rubber to the connective end of the lens (obviously not on any contacts etc) to combat the problem - and was wondering if anyone had tried something similar - or has some other remedy?