(Click to enlarge)

Correct me if I'm wrong, but that's either your zone's header text, or your site name. If you hover the mouse on the tab the page title is at the end. In HTML_HEAD.tpl the <title> is produced by appending stuff...

<title>{+START,IF_NON_PASSED,TITLE}{+START,IF_NON_EMPTY,{$HEADER_TEXT}}{$HEADER_TEXT*} &ndash; {+END}{$SITE_NAME*}{+END}{+START,IF_PASSED,TITLE}{TITLE}{+END}</title>

It's not in a zone, it's the start page of the site but it's using the page title from the child page. Wasn't like that before updating to the latest version.

Automated response: Comcode page titles may leak into other Comcode pages when main_comcode_page_children used

This does not seem to affect most installations, occurring with some combination of cache settings and cache order. Therefore this is a speculative fix, but it does clean up the code in the right way.

After uploading Hotfix files:

PHP NOTICE [8] Undefined index: COMCODE_PARSE_TITLE in sources/global3.php on line 468 (version: 10.0.10, PHP version: 5.6.32, URL: /index.php?page=login&type=login&redirect=http%3A%2F%2Fsurfrenzy.net%2Findex.php%3Fpage%3Dstart)

Sorry, I updated the archive with a new sources/global3.php.

I also forgot to say you might need to empty the Comcode Page cache.

I emptied the cache folder manually so didn't need to empty the Comcode Page cache. Fix worked a treat, thank you.