Hi there!
In general, pointing a single IP address at another CDN for a Netlify site can cause issues. As we maintain our set of servers, the IPs that are used sometimes change as we do things like perform maintenance and scale capacity up and down. These changes are reflected in our published DNS records.
There’s some additional information available at [Support Guide] Why not proxy to Netlify? which covers some of the challenges with putting another CDN in front of us.