Yes, they all originate from the FB network. With ipV6, it’s visible at first glance, for example: ‘2a03:2880:21ff:c::face:b00c’. We are trying to rate limit. But then the page previews stop working when sharing posts on FB.

The OG cache most likely only needs to be set once, so it's safe to block any requests after the initial request to a specific URL

We have no problem with multiple requests for a specific url. Our application runs thousands of domains. FB seems to scrape them all and completely. The problem is intensity.

Could be bad actors abusing the Sharing Debugger or the API that allows requesting a cache refresh. However, FB won't tell you so rate limiting the user agent is your best/only option.