This is not a bug as such ......
When you scan for missing files across your collection and your collection is located on various drives/locations - When the scan is complete a popup box with the drive letters and the number of missing files per drive is shown. The first drive is selected and you are unable to group select all drives. If you just select one, a pop up box is shown with the files, this can be Ok'd and the missing from this drive are removed correctly from the database. Problem here is then that the window closes and you have to re-scan again to select the next drive and so on. Strangely though, from the first drive select screen, if you select the cancel option, all the files across all of the disks are then displayed and you can correctly remove all of the missing files.
So not a bug, more illogical than anything