I've encountered this as well. My multi-lingual text is different than yours.

It's Armenian and Mandarin. When asked about it, Codex will translate the Armenian, the but Mandarin causes it to go into a frenzy, repeatedly attempting to maybe perform the same task again? It will not translate it. Even if mentioned in a sentence, the frenzy begins. I tried it four or five times in a row, with conversation in between. It feels like the Manchurian Candidate or something.

In a new session, Codex is unaffected when encountering the text.