Deleting a network in VMware Cloud Director returns "Bad Request: Error occurred in the backing network provider"

Products

• VMware Cloud Director

Issue/Introduction

When attempting to delete a network in VMware Cloud Director an error is returned with:
[###########################] Bad Request: Error occurred in the backing network provider: The path=[/infra/tier-1s/#######################] is invalid, error code 500012

Environment

VMware Cloud Director 10.6.x

Cause

The segment and tier-1 gateway were deleted directly in NSX-T outside of VMware Cloud Director.

Resolution

Capture a database backup following Backup and Restore of Your VMware Cloud Director Appliance. 
Open a support request with Broadcom VCF Support referencing this KB article and upload the backup to the support request with the error message and stack trace, or include a new support bundle with the timestamp of the error.