Yes, I saw the site a couple times and then back to a 521. Plugins are not going to affect this unless you have a mis-configuration in SSL. I work on NGINX setup’s so htaccess means nothing except you can push rewrite rules through it. When I mention a page (rewrite rule) to force non-www (which is what I’m thinking you’ve done) understand the reason which is lost to many is www in fact is a sub-domain and why we point it to no www. The reason is, if your site worked on both www and non Google and crawlers would see 2 separate websites and in addition to terrible seo it’s confusing (or can appear broken) to people/browsers. If you’re doing this with .htaccess I believe it’s working but as you say intermittently. If this page rule is in Cloudflare, they have a guide for that and if so and it’s working right you don’t need both that and the .htaccess. I’ve seen both .htaccess and Cloudflare page rules get real fussy because of how some of the guides are with wildcards like www.domaindotcom/ and domaindotcom/ pointing to https://domain.com/$1 or /$2 (you have to read the guides to get my drift more).
My question now is - Are you using “Flexible SSL” in the SSL/TLS app of Cloudflare? If you are you may want to read about this plugin (I used to use this successfully, before I began installing SSL certs on my machines) - Flexible SSL for CloudFlare – WordPress plugin | WordPress.org English (Canada)
somehow Cloudflare is stripping the asterisks off the above because of markup *www.domaindotcom/* and *domaindotcom/*