Time Machine backup fail

bekminor from saintlouis wrote:

"there is insufficient free space on the backup disk"

Start a new backup with a new drive...

erase the existing TM drive and start a new backup...

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Back up your Mac with Time Machine - Apple Support

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology.

Consider the possibility the backup disk has insufficient free space.

Read If you can't back up or restore your Mac using Time Machine - Apple Support.