unable to delete a user

I am the primary user and even though I sign in as the primary, I have been unable to delete a secondary user account. This secondary account receives billing emails but I only want those emails going to my main account address instead of both.

When I attempt to delete the secondary user, an error usually occurs that will not allow the deletion.

On some attempts, the secondary user appears to get deleted, but when I next log in that user is back.