After implementing subresource integrity and switching over to CloudFlare, I noticed resources like CSS and JavaScript were breaking on my site. I ran into the same issue as this guy. CloudFlare presents these options and I didn't think twice about turning them on.

CloudFlare interface showing three checkboxes for 'Auto Minify'...HTML, CSS, and JS

Because there's an integrity hash on these files, they fail to load when modified. CloudFlare's 'auto-minification' changes, causing the hash check to fail.

After turning off these optimizations, CSS and JavaScript started loading again (after purging the cache). I still want to minify my CSS and JS, but I'll have to implement it on the server side.