This is a bug that is hunting me for a while
every time for unknown reason the small image that previews presets gets stuck on one of the images and can not be switched
so I need to restart the software to get this resolved .
im running last Version Lightroom CC on mac OSX 10.11.6
Are you using the latest version of Lighgroom CC 2015.7?
Do you mean that the Preview panel gets stuck on a specific image or preset?
thanks for letting me know .
I just updated , will comment if recreated