Chrome 64 Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet': Cannot access StyleSheet to insertRule

We believe this commit to Chromium to be the root cause of our issue:

Update behavior of CSSStyleSheet to match spec for Security origin

The quick solution for us was to simply reorder the CSS. It seems that previously the culprit plugin was inserting CSS rules to this remote CSS:

<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:300,400,700">

Simply reordering our stylesheets to ensure a script from our site was in first position (document.styleSheets[0]), fixed the issue:

<link type="text/css" rel="stylesheet" href="/Public/js/jquery-ui/jquery-ui.css" />
<link type="text/css" rel="stylesheet" href="/Public/js/jquery-ui/jquery-ui.theme.min.css" />
<link type="text/css" rel="stylesheet" href="/Public/css/msgPop.css" />
<link type="text/css" rel="stylesheet" href="/Public/js/select2/select2.css">
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:300,400,700">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css">