The result was that the page display was wrong and Google Analytics code did not trigger.
If you know a page was not being returned, you can use Fetch as Google in Google Webmaster Tools to "see a page as Google sees it". This will give you an idea of what HTML code is being returned, and the HTTP status codes being returned by your server.
If the Google Analytics code is not being triggered, it either was not fully downloaded and executed, or your server returned error pages (e.g., 40x and 50x status codes instead of 200), which do not contain tracking code.
If the former is the case, then make sure your tracking code appears in the head section of your pages just before the closing
</header> tag, as covered here: Google Anayltics - How to set up the web tracking code
If the later is the case (i.e., error status codes were returned), then you can track these occurrences by adding the tracking code to your server's error pages, as covered in these two sources:
Tracking Error 404 Pages and Broken Links in Google Analytics
How To Track 404 Errors in Google Analytics
Lastly, it's quite possible that the WordPress cache plugin is causing the issue, so uninstall/disable this plugin and retest your pages with Fetch as Google again to see if the problem goes away.