Work-around: Restart camera via GUI, Administration>Maintenance>Restart, it should come back working until the sliders freeze up again. Only seems to happen to some cams, may be a factory setting is off for zoom or focus ranges. Out of all the 2600 cams i've installed i find that the focus and zoom ranges are different for each camera, sometimes very different, sometimes i cannot set two cameras to the same FoV near the extremes.
Update: Cisco FA confirmed cams stop streaming, they're looking into why.