With "development mode" disabled access to website is slow from some provider

Hello, we are getting an issue, basically we have different performance based on the provider that is connecting to our website.

For some reason, seems some provider are slowing down the connection to Cloudflare. We’ve temporarily solved this by activating the development mode, but actually we want understand if someone else is experiencing this issue and how we can manage it.

We’ve tried to purge the entire cache and disabled the development mode, but issue is still there.