After upgrading to NSX 4.2.0, it was observed that existing NSX logical segments were replicated on a separate Distributed Virtual Switch (DVS) that is not configured within the NSX host profile.
This separate DVS was previously created for the NVDS to CVDS migration to address an issue detailed in the KB article below.
VMware NSX-T Data Center
VMware NSX
The root cause of this issue has yet to be determined.
Please open a service request to Broadcom Technical Support and referencing this KB article for assistance.