This type of error message could arise due to various reasons. As it stands, it may prove difficult for us to provide a concrete reasoning behind it, as well as a proven solution to mitigate it. In order for us to mitigate this in a timely manner and provide you with the support you need, could I ask that you create a
Issue Tracker entry outlining the issue at-hand? As this issue will be created in a private component, feel free to provide your project id as well, so that we can investigate your Cloud SQL instance thoroughly and perform the necessary actions to identify the root cause of this issue, as well as resolving it.