Just did a test because when I try to access Yoast sitemap /sitemap_index.xml, server resources (CPU + RAM) are both exhausted to 100% until server generate 542 error)
During this period of time, all my sites on this cloud server were reported dead by JetPack. Until 5 minutes after I close the tab which was trying to open the sitemap, server go back online again.
So I turned off all plugins and turn it on one by one starting from GD core, now locked down the Location manager is the killer.
Please try and see if you can duplicate the issue. If required you may test it with my site.
I do need Location manager feature for the project, so I just submit the sitemap_index.xml to Google and I will turn the Location Manager back on.Not sure if Google saved the sitemap file or just save the link.
Great if you guys can figure out the cause and fix it asap.
cheers
Sam