Empty folders in Notes reappear after deleting

I have been trying to delete a few empty folders in Notes (iCloud) and when I do, the notes simply re-appear on all devices. Here's what I've done, to no avail:

1. Turned off iCloud Notes all my devices, so there are now no notes showing on any of those devices in Notes.

2. Log on at iCloud.com and attempt to delete there.

After deleting, the notes simply reappear a few minutes later when I refresh the page at iCloud.com.