This page emits an ETag in the classic Apache inode-leak format:
ETag: "2b3f-65012285dc0d6-0a1b2c3d4e5f"
The format is <size-hex>-<mtime-hex>-<inode-hex>, the default when Apache has FileETag INode MTime Size. Load-balancer setups leak which backend served the request because each backend has a different inode number.
Expected trigger in analyzer 030_response_headers: