If you remove a cPanel user using a Linux command such as 'userdel' WHM will show the account in List Accounts, but upon attempting to remove it, it will show an error: Account does not exist.
To avoid this issue, use only WHM to remove cPanel accounts.
Readding the user via the command 'useradd' fixes the issue. After that, you can use WHM to remove the account correctly. Example command: