I just replaced my MacBook Pro and installed PM. I am now seeing irregularities when marking and un-marking the color class on photos. For example; if I select all images in a folder and re-set the color class to 'none,' a few images retain their original color class. Also, after marking a few dozen images with a particular color, if I isolate just that color class, only a few of the marked images display. I have never had any trouble like this before. Is there something simple that I am missing? I am running OS X 10.13.6, and PM version 5.0, build 19695 (4a8c3fe) on a new (2018) 15" MacBook Pro.