I am at my wits' end with this issue. Maybe someone somewhere has an idea of how to help?
I am seeing constant 503 errors on my site. They show up intermittently after clicking around to different pages on the frontend and backend of the site. Sometimes it takes one or two clicks, and other times it takes 15-20. They go away after refreshing the page. My GoDaddy Pro account shows the site is constantly down dozens of times a day in the Uptime Monitor, and the Performance section also shows an "F" rating under YSlow due to a 503 error.
Things I have tried:
Disabled the theme by switching to Twenty Twenty One theme.
Disabled all plugins.
Removed all custom PHP in my functions.php file.
Enabled debug mode and have resolved all of the PHP notices and warnings.
Ensured CDN is disabled.
Contacted GoDaddy support over a dozen times, and they can't figure it out, but keep trying different things. They have tried "resubmitting" the site, clearing the site's cache, killing all processes, resetting permalinks, increased resources, and still the issue occurs. I was also told it's an ISP issue, but it is happening with everyone I speak to with different ISP's. This morning they told me "The php processes are getting exhausted so killed those but this will happen again and you really need to check the plugin which is causing issue..."