google-cloud-php: URGENT: [composer] GRPC randomly throws ServiceException("Socket closed")

@dwsupplee @jdpedrie this issue still randomly persists.

URGENT REQUEST. We’re part of the Google Cloud Startup program and launching this year… a fix would be greatly appreciated so we can move to production.

Log output:

PHP Fatal error:  Uncaught Google\Cloud\Core\Exception\ServiceException: {
    "message": "Socket closed",
    "code": 14,
    "status": "UNAVAILABLE",
    "details": []
} in /[...]/Google/composer-google-cloud/vendor/google/cloud/Core/src/GrpcRequestWrapper.php:257
Stack trace:
#0 /[...]/Google/composer-google-cloud/vendor/google/cloud/Core/src/GrpcRequestWrapper.php(194): Google\Cloud\Core\GrpcRequestWrapper->convertToGoogleException(Object(Google\ApiCore\ApiException))
#1 [internal function]: Google\Cloud\Core\GrpcRequestWrapper->handleStream(Object(Google\ApiCore\ServerStream))
#2 /[...]/Google/composer-google-cloud/vendor/google/cloud/Firestore/src/SnapshotTrait.php(122): Generator->current()
#3 /[...]/Google/composer-google-clo in /[...]/Google/composer-google-cloud/vendor/google/cloud/Core/src/GrpcRequestWrapper.php on line 257