Rocket Validator automatically checks your pages on the W3C Validator.
HTML issues tagged as user-scalable.
<meta name="viewport"> element has been found where the allowed values for the viewport prevent users from zooming and scaling the document.
user-scalable="no" parameter disables browser zoom on a web page. The
maximum-scale parameter limits the amount the user can zoom. Both are problematic for users with low vision who rely on browser zoom to see the contents of a web page. Consider relaxing these values in order to allow users to resize the documents.
When was the last time you validated your whole site?
Keep your sites healthy checking for A11Y/HTML issues on an automated schedule.