Gemini-2.5-flash-native-audio-preview-09-2025 issue in function calling Internal error occurred

Working fine on gemini-live-2.5-flash-preview. Upgraded to new model but working fine for normal queries when went to function calling query, it throws onclose. We have a deadline and need to upgrade for further testing and development. Sometimes it works for function calling but most of times it fails. I have tier-1 account.
onclose: async (e) => {

 console.log(\`\[${sessionId}\] Gemini session closed:\`, e?.reason || '(no reason)'); const ctx = sessionContexts.get(sessionId); broadcast(sessionId, { type: 'status', message: 'Gemini session closed' }); } 

\ Gemini session closed: Internal error occurred.