When I select some thumbnails and move them by dragging to another part of the contact sheet the view jumps to a different part of the contact sheet. Instead of showing the part where I moved the images it shows a completely different part.
This happens with PM 4.6.3 on OSX 10.5.8 some 2000-3000 images opened into the contact sheet but most of them hidden with color classes filtered out currently showing only some 700 of them.