Those errors are usually caused by CloudFlare automatic Front-end Optimization (FEO) stuff, like trying to losslessly optimize images, add cache control, gzip, SPDY/HTTP2, etc. It used to be a primary marketing point, and while its still there (and still causing problems) they have moved away from promoting it so much.
Its best to use of them as a CDN, DDoS sink, and SSL. Their other stuff like FEO or their web app firewall stuff really isn't that impressive enough to be considered a reason for switching.
Disclaimer: I work in the web performance space, and used to work in the web security space. As a whole I'm not a fan of the "stick a magic appliance in front of a website to automatically stop [web security issues | web performance problems]" approach, whether from CloudFlare or otherwise.
Its best to use of them as a CDN, DDoS sink, and SSL. Their other stuff like FEO or their web app firewall stuff really isn't that impressive enough to be considered a reason for switching.
Disclaimer: I work in the web performance space, and used to work in the web security space. As a whole I'm not a fan of the "stick a magic appliance in front of a website to automatically stop [web security issues | web performance problems]" approach, whether from CloudFlare or otherwise.