Things would be tons easier if you can simply erase the Time Capsule disk and then start over again with new backups for the Mac(s) that you are using at the present time.
Post back if you can consider this and need more instructions.
As far as "bands in use", I am not able to duplicate that error, so another user will need to help on that issue.
- How are you disabling the TC
Click on the Time Machine "clock" icon at the top of the Macs screen
Click on Open Time Machine Preferences
Uncheck the box next to Back Up Automatically
No backups will occur unless you choose to back up manually, or you enter a check mark again in the box next to Back Up Automatically
- Where can I find the spares bundle?
Click on the "smiley face" Finder icon on the dock on your Mac
Click on the Time Machine icon under the Locations listing on the left panel of the Finder window
Double click on the Time Capsule disk in the window to the right......(named "Data" unless you have changed the name)
Click Connect or it might read as Connect As
You may be asked for the Time Capsule administrator or base station password when you do this
If instead of a "sparsebundle" file, you see a "backupbundle" file, this indicates that the Catalina operating system has been installed on the Mac in question. Apple has made a number of undocumented changes with Time Machine in Catalina, so unfortunately all bets are off if you have installed Catalina.