It seems like you are experiencing intermittent timeouts which could be caused by cold starts or concurrency saturation. There could be delays caused by cold starts if there are bursts of requests and despite setting the maxInstances to 30. Try setting the minInstances to 1 so that there is always a warm instance ready to handle requests.

Additionally, consider increasing your concurrency if a large number of requests comes beyond your concurrency limit as some requests may be queued.

You can also take a look at this Google Cloud Community discussion for helpful insights.