Time Machine bug - not enough space, folder cannot be deleted
You can try this method. it has worked in the past. Open your Time Machine backup disk and then Enter Time Machine using the Time Machine icon in the menu bar. Now you should be in Time Machine with a list of the backups. Select one of the backups and then look for a gear icon near the header of the backup you selected. Click on this gear icon and it should have an option to delete that backup. If you open a Time Machine folder you can use the gear icon to delete that folder. Here is what the gear icon looks like: