Time Machine BUG: Without warning, one or more of your disks stops being backed up...

Question

Hi all
Just discovered an interesting and potentially dangerous bug in TM running 10.7.4 (like many others I've downgraded from 10.7.5 because of the Spotlight/TM problems noted in this forum).
Here's the bug: You set up TM and specify certain items -- files, folders or volumes -- to be excluded in the "Options" pane of TM Preferences. If you exclude a volume (e.g. a cloned backup volume), that volume must of course be mounted in order for it to be added to the "Exclude" list. But if you subsequently umount the excluded volume, TM SIMPLY REPLACES IT WITH SOME OTHER MOUNTED VOLUME without warning. The result: unknown to you, one of your disks, that you think is being backed up, isn't. You can actually see this happen if you unmount the disk you want to exclude while your exclusions list is open.
This bug is 100% reliable. Tried permissions repair, clear caches, verify backups, reset TM by deleting /Library/Preferences/com.apple.TimeMachine.plist and re-entering excluded items -- same result.
Question: Have others found this bug? Has anyone found a way of adding a volume to the TM exclusions list so that it "sticks" regardless of whether or not the volume is mounted??
The only workaround I can see: Never unmount any disks in your exclusions list -- if you do, something else will be excluded instead. If like me you want easy access to the disks you work with but not others (e.g. backup clones), one option is to make the excluded disk mounted-but-not-visible.
Appreciate others comments before reporting to Apple in case there's something weird in my setup (don't think there is).
Pondini: Checked your great site, couldn't see this noted - apologies if I missed it.
Ta much.

Answer 1

For Windows 7 I corrected the problem using the steps below.  Since Windows 8 is setup for touch screen you will need to find these controls. 
Corrective Action.  Note that several of these steps require the computer to process the action and may take 20 minutes to complete, depending on the configuration. 
DELETE INTERNET EXPLORER PERSONAL RECORDS
(This step may not be necessary)
Start Windows Operating System (OS) in Safe Mode (Restart windows using F8)
Select “Start” button
Select “Control Panel”
Select “Internet Options”
Select “Advanced” tab
Select “Reset” tab for “Reset Internet Explorer settings”
Select “Delete Personal Records”
Select “Reset”
DISABLE INTERNET EXPLORER
If not in WINDOWS SAFE MODE start Windows OS in Safe Mode (Restart windows using F8) Select “Start” button
Select “Control Panel”
Select “Programs and Features”
Select “Turn Windows Features On or Off” (Left pane)
Uncheck IE# checkbox (# will be the IE version number)
Select “OK”
Reboot the computer
RE-ENABLE INTERNET EXPLORER
Windows OS will restart in normal mode, or select normal operation
Select “Start” button
Select “Control Panel”
Select “Programs and Features”
Select “Turn Windows Features On or Off” (Left pane)
Check “IE# checkbox” (# will be the IE version number)
Select “OK”
Reboot the computer
RESTORE YOUR DESKTOP
Select “Start” button
Select “Control Panel”
Select “System & Security”
Select “System”
Select “System Protection”
Select “System Restore”
Select “Chose a different restore point”
Select a restore point at least 2 weeks ago (Check “Show more restore points” checkbox, if necessary)