Openfire re-uses the origin-id for stanza-id
XEP-0359 §2.2: "The server or component MAY add a <stanza-id/> element. In that case, it MUST preserve the content of the <origin-id/> element."
As well as preserving the content, Openfire currently reuses the content as its own "stanza-id".
Openfire should preserve the origin-id, but generate its own unique ID, else risk conflicts by trusting all clients to generate globally unique values.