(DNS lookup, Initial connection, SSL negotiation) randomly missing


I have a private instance, which a PHP script hits every few minutes. When looking at the waterfall graph, in regards to the first connection that fetches the HTML, it appears that first three phases(DNS lookup, Initial connection, SSL negotiation) are not showing up consistently. During some runs they are there, during some they are not. What determines that? One thing is consistent is that if one of the 3 is missing, then the other two wont show up as well, in that case the request only reports ‘Time to First Byte (TTFB)’ and ‘Content download’.

These are the args I run it with:
‘url’ => $url,
‘f’ => ‘json’,
‘iq’ => ‘80’,
‘pngss’ => ‘1’,
‘video’ => ‘1’,
‘location’ => ‘EC2-WPT_wptdriver:Chrome’

Please let me know if I’m missing something obvious.
Thank you.