wp-stateless: Profiling slow page generation - wp-stateless accounts for over 37% of page generation time

I’m profiling a website to figure out what’s causing long (> 1s) page generation times. I’ve identified wp-stateless as one of the culprits, as it accounts for 16.76% of the cost. The problematic calls are:

wpCloud\StatelessMedia\Bootstrap->_convert_to_gs_link @ 654 - 10.74%

$meta[$key] = $this->_convert_to_gs_link($value, $image_host, $baseurl, $file_ext);

wpCloud\StatelessMedia\Bootstrap->convert_to_gs_link @ 636 - 6.02%

$updated = $this->_convert_to_gs_link($meta, $image_host, $baseurl, $file_ext);

Has anyone else profiled a website and identified the same issue? Any ideas why these 2 functions are slowing down page generation so much? And any ideas on how to speed them up, perhaps with object caching?