Hi,
In that case, you might need to capture some dumps or traces to further investigate the issue, which I suggest to contact Microsoft Customer Support and Services where more in-depth investigation can be done so that you would get a more satisfying explanation and solution to this issue.
You may find phone number for your region accordingly from the link below:
Global Customer Service phone numbers
https://support.microsoft.com/en-us/help/4051701/global-customer-service-phone-numbers
Thanks,
Eleven