Plus Google uses algorithms to assess "mobile-friendly pages" which are not 100% accurate.
For example, I see Google warnings all the time about responsive forum (not just Xenforo) and WordPress sites complaining that some of the text is too small or that "elements are too close together" (presumably buttons), but checking those sites invariably leaves me thinking "what the heck are you talking about?", not to mention that users seem to have zero difficulty using those sites on even small mobile devices.
and if you process the page again, google would show no problems. i have seen this happen multiple times but on a third party theme. i switched to bundled default few weeks ago and errors have more or less disappeared.
yeah. i have been thinking it could be a rendering issue because my vps choked out at that particular moment. i also see random errors related to 404s on pages in sitemap that are very much alive and loading fine on manual checks.