Hello Yousuf,
I understand that you do not see 500 error messages in the Stackdriver Error Reporting. You may find this document helpful as it provides troubleshooting steps for your issue.
However, if you still experience the issue after following the troubleshooting steps provided in the aforementioned document, please open a new issue in Issue Tracker and we will be happy to troubleshoot it further.
Note that Google Groups are reserved for general Google Cloud Platform-end product discussions and not for reporting issues.