CacheStaleOnError and CacheIgnoreHeaders interaction for stale error responses

Configuration Goal

When the origin server returns a 5xx error and CacheStaleOnError is enabled, Apache serves a stale cached copy. The administrator wants to ensure that any headers listed in CacheIgnoreHeaders are removed from that stale response, just as they are for fresh responses.

Current documentation does not clarify whether CacheIgnoreHeaders is applied to the stale content delivered under CacheStaleOnError, leaving the behavior uncertain.

• Does CacheIgnoreHeaders strip headers from stale responses served due to CacheStaleOnError?
• If not, what configuration or directive would be required to achieve header stripping for stale error responses?
• Are there any known side‑effects or performance implications of applying CacheIgnoreHeaders to stale content in this scenario?