When present in an HTTP response, the stale-while-revalidate Cache-Control extension indicates that caches may serve the response in which it appears after it becomes stale, up to the indicated number of seconds since the resource expired.
If Always Online is enabled, then the stale-while-revalidate and stale-if-error directive are ignored.
The stale-if-error Cache-Control extension indicates that when an error is encountered, a cached stale response may be used to satisfy the request, regardless of other freshness information.
The stale-if-error directive is ignored if Always Online is enabled or if an explicit in-protocol directive (e.g., by a no-store or no-cache cache directive, a must-revalidate cache-response-directive, or an applicable s-maxage or proxy-revalidate cache-response-directive) is passed.
From that, it seems if you able Always Online https://support.cloudflare.com/hc/en-us/articles/200168436 it might be what you want in case of origin issues ?
and control from origin
Alternatives to globally enabling Always Online include:
- Using Cloudflare Page Rules to enable Always Online, or
- Allowing your origin web server to determine which content to cache for display if your origin web server is offline:
- Disable Always Online,
- Set Origin Cache Control for your resources, and
- Enable stale-if-error at your origin.