Nano Banana (Gemini 3.1 Flash Image) 503s with tier-1

hi - I’ve integrated nanobanana into my app and am testing with a pretty low rpm (one user at a time making no more than 5 rpm) and i get 503s all the time (like one out of every 5 or so requests. I’ve also implemented 3 retries and still can’t get it to be reliable. Am I doing something wrong or is this because it is pre-production? I am happy to upgrade to tier-2 if it helps