Hi @dtinth , had the same issue, described here: Gemini-1.5-flash is no longer processing audio files (500 Exception) - retry does not help - #5 by Siva_Sravana_Kumar_N
I saw exactly the same behaviour as you, started about a week go, with increasing error rates. Clearly an issue in the backend.
As per my message in the other thread, my workaround is switching to the flash-2.0-lite.