Guest account requires password - Disabling/reenabling doesn't work

There are many threads here and elsewhere describing an issue where the Guest account suddenly starts prompting for a password, however in my case disabling and reenabling the Guest account (the solution suggested in all of those threads) does not work.

When attempting to log into my guest user account via fast app switching the Guest User panel appears as shown below and a loading spinner displays and conintues spinning indefinitely. Also note that an authentication window pops up behind the Guest User panel.

In order to remove the Guest User panel I have to press the power button once to turn off my screen, wake my computer and then press Cancel (I'm not able to log in to the Guest account with any - or no - password). The screenshot below shows what I see after waking my computer.

Attepting to log in to the Guest account from the login screen causes the same authentication window as mentioned above to appear, and although this time I am able to enter my password the computer rejects anything I type in. After cancelling the authentication window I am again able to attempt to log into the Guest account, and again no passwords are accepted.

I have tried various combinations of restarting my computer and enabling and disabling the Guest account but have had no success. I also tried right clicking the Guest User in System Preferences>Users & Groups, clicking Advanced Options and deleting the entry for the Guest account's home directory. That wasn't my smartest move, as it turns out, as now clicking Advanced Options on the Guest User does nothing. Below is the output from a relevant Terminal command:

dscacheutil -q user -a name guest

name: Guest

password: ********

uid: 201

gid: 201

dir: /var/empty

shell: /bin/bash

gecos: Guest User

I'd like to try and resolve this without doing a clean install, but obviously that's my last resort. Any help would be greatly appreciated.