A backup for my backup

I’m having problems with my Time Capsule that result in worrying error messages when it attempts to run a backup. I don’t trust my current backup state, but I don’t want to discard what backups there are in order to make a fresh backup, in case that fails, too. How can I force Time Machine to make a full backup without deleting the existing ones? Jonathan Gough Create an interim Time Machine backup on an external USB disk, erase and restart your Time Capsule backup. Once Time Capsule’s behaving itself, erase the USB backup.