Denis Ryabov

There are several way to deal with render blocking:
– generate and embed “above-the-fold css”, and load other styles asynchronously;
– merge javascripts and load them either at the end of html, or asynchronously (there are some heuristics to choose where it is appropriate);
– transform known synchronous javascript codes (Facebook, Twitter, Google +1, ShareThis, etc.) into asynchronous ones;
– load all javascripts asynchronously (with emulating of document.write for synchronous embedded scripts), it is the option named “Non-blocking Javascript” in plugins’s advanced settings.

Most likely it is related to lazy loading of iframes, we will try to reproduce and fix it soon.

Could you send us (hello at pagespeed.ninja) a screenshot of “unreadable text”, maybe it will allow us to catch the error.

1. On which tab do you have this message, in General or Advanced?

2. What IE version do you use for test? Try to disable gzipping in Advanced tab, maybe your server compresses html itself.

I would recommend you to disable all of PageSpeed Ninja optimization, and then enable them one-by-one and re-check scores in Google Page Insights to found which optimization is related to 500 error. Note that Google Page Insights caches results for “few minutes”, so it is necessary to either re-check with few minutes interval, or add a dummy query to URL, e.g. https://rakhioverseas.com/?test1 .

And what web server do you use? HTTP headers say it Apache, but the header may be set arbitrary. If it is Apache, which version, 2.2 or 2.4? And how PHP is called, as Apache module or via FastCGI?

Additionally, you could try to enable Error logging in Troubleshooting section of Advanced tab of PageSpeed Ninja settings, it will store all errors, warnings, and notices to wp-content/plugins/psn-pagespeed-ninja/includes/error_log.php, maybe it will be possible to found something related there.