Right, I have managed to delete the old CPT and get the new one working. However, the old CPT is still appearing as a ghost in the menu and it has a typo which may be the original cause of the problem. I have tried removing it with a flush of the rewrite rules table, but that did not work.
I have attached the references from phpmyadmin below. Any idea what to do without knackering the DB?
s:37:"treaments/
[^/]+/attachment/([^/]+)/?$";s:32:"index.php?attachment=$matches[1]";s:47:"treaments/[^/]+/attachment/([^/]+)/trackback/?$";s:37:"index.php?attachment=$matches[1]&tb=1";s:67:"treaments/[^/]+/attachment/
([^/]+)/feed/(feed|rdf|rss|rss2|atom)/?$";s:49:"index.php?attachment=$matches[1]&feed=$matches[2]";s:62:"treaments/[^/]+/attachment/([^/]+)/(feed|rdf|rss|rss2|atom)/?$";s:49:"index.php?attachment=$matches
[1]&feed=$matches[2]";s:62:"treaments/[^/]+/attachment/([^/]+)/comment-page-([0-9]{1,})/?$";s:50:"index.php?attachment=$matches[1]&cpage=$matches[2]";s:43:"treaments/[^/]+/attachment/([^/]+)/embed/?
$";s:43:"index.php?attachment=$matches[1]&embed=true";s:26:"treaments/([^/]+)/embed/?$";s:42:"index.php?treaments=$matches[1]&embed=true";s:30:"treaments/([^/]+)/trackback/?$";s:36:"index.php?treaments=
$matches[1]&tb=1";s:38:"treaments/([^/]+)/page/?([0-9]{1,})/?$";s:49:"index.php?treaments=$matches[1]&paged=$matches[2]";s:45:"treaments/([^/]+)/comment-page-([0-9]{1,})/?$";s:49:"index.php?treaments=
$matches[1]&cpage=$matches[2]";s:34:"treaments/([^/]+)(?:/([0-9]+))?/?$";s:48:"index.php?treaments=$matches[1]&page=$matches[2]";s:26:"treaments/[^/]+/([^/]+)/?$";s:32:"index.php?attachment=$matches
[1]";s:36:"treaments/[^/]+/([^/]+)/trackback/?$";s:37:"index.php?attachment=$matches[1]&tb=1";s:56:"treaments/[^/]+/([^/]+)/feed/(feed|rdf|rss|rss2|atom)/?$";s:49:"index.php?attachment=$matches[1]&feed=
$matches[2]";s:51:"treaments/[^/]+/([^/]+)/(feed|rdf|rss|rss2|atom)/?$";s:49:"index.php?attachment=$matches[1]&feed=$matches[2]";s:51:"treaments/[^/]+/([^/]+)/comment-page-([0-9]{1,})/?$";s:50:"index.php?
attachment=$matches[1]&cpage=$matches[2]";s:32:"treaments/[^/]+/([^/]+)/embed/?$";
