Irregular (slow) page loading with advagg enabled -- reading response body failure

I'm wondering if anyone else has been experiencing issues like this.

When accessing pages (ostensibly not cached) as an anonymous users, I get the situation where the page renders (all elements visible, styled, and functional) but the browser indicates that the page is still loading. After a minute or so, the request stops (see incorrect-response.png, attached). If I proceed to refresh the page, it fully loads as expected (see correct-response.png, also attached).

The attachments are from Opera's network log which is built in to Dragonfly. Using Chrome developer tools, the result is similar but the output just says that GET failed (see chrome-failed, attached).

Config/site details:

• nginx
• Drupal 6.26
• Enabled performance mobules -> boost, advagg, advagg_bundler, purge, expire

If I can provide anymore information or troubleshooting, please let me know.