OK, I've updated the Memory Cache setting to 768MB, and I've changed the default sort to "by filename." I've also changed the actual applied sort in the contact sheet to "filename," and relaunched PM to make sure everything sticks.
OK, so what takes place when you switch out of PM before you switch back in?
I'll give you an example. At this moment I can go to PM, hit <alt> <tab> to flip to this window in Chrome, then
immediately <alt> <tab> back to PM and it triggers. It doesn't matter which other app I switch to, or that I do nothing there. The switch alone seems to cause it.
Changing the default sort and memory cache doesn't seem to have helped.
Oh and I've just verified that the same behavior occurs from the contact sheet window as well.
Not sure if this is relevant, but my contact sheet is "folder and subfolders."