While defragmenting it shows "Defrag progress" popup which is now modal and therefore prohibits change of tabs in the background. This used to work just fine for a long time.
I usually defrag files only, and as I cannot scroll up/down in the file list, I switch to the drive tab, so I can see more detailed progress of how many files and fragments are left to be defragged, but with the most recent version that's not possible anymore.
Furthermore, I'd love to be able to change any tabs and scroll the list while any message dialog is popped up.
See also thread http://forum.pirifor...12 which someone else raised independently of you. I'd come to the same conclusion as you that the "Defrag progress" popup has accidentally been made modal in the latest V2.16.809 version.
Has this bug been officially confirmed and logged by the support team at Piriform? I'm surprised there hasn't been an update, incorporating a fix for this regression bug first noticed in the current version, 2.16.809.