V8.4.0

I'm likely missing something simple but I have two pages, same theme, pagetype and template, all caching is off in the Dash as it's a dev site currently yet I'm getting two very different css tags being output which makes the pages look different. Using <?php echo $html->css($view->getStylesheet('main.less')) ?> in the header_top file to output these elements.

One page's tag is:
<link href="/application/files/cache/css/myproject/main.css?ts=1530538741" rel="stylesheet" type="text/css" media="all">

And the other:
<link href="http://dev.mytest.co.uk/ccm/system/css/page/1/main.less" rel="stylesheet" type="text/css" media="all">

There's no custom stuff set on the first (incorrect appearance) page, it's only just been created. If I clear the cache then the first url becomes invalidated and another main.css link is generated next page load.

Any clues?