This is what I get in the Chrome timeline when I inspect - which, while it is accurate (600ms) that /api request stays pending for 10-60 seconds before it goes through.
Server logs show that the response is sent out in < 100ms so 600ms over mobile seems reasonable.

The culprit may be an adsense code block that I have in the widget area. Removed it and things seem to be faster. Need to nail this down and get it to fail / work consistently. (The init code is in the header via the custom header / css config.
<div style="text-align: center; height: 280px; min-width: 300px; max-width: 336px; margin: 10px auto; padding-bottom: 10px;">
<!-- 2015 - NewsFora V3-->
<ins class="adsbygoogle"
style="display: block;"
data-ad-client="ca-pub-xxxx"
data-ad-slot="2701930026"
data-ad-format="rectangle"></ins>
</div>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>