NVP vProxy: VM backups from stand-alone ESXi fail with "Received an HTTP code: 400...."

A stand-alone ESXi host was added to NetWorker (no vCenter server).

The ESXi host is at version 7.0U3.

vProxy version is at 4.3.0-46.

The ESXi host was added using root account and "deployed in cloud" option (required):

Figure 1: Screenshot of Modify vCenter page

VM backup action immediately fails with the following error message in the action log:

Figure 2: Back up action failure message in Action log

Error message:

07/13/2023 09:35:56 AM rhelvm8: Unable to start backup on vProxy 'vproxy02.emclab.local': Received an HTTP code: 400, libCURL message: "", vProxy message: "Error received from vProxy ="-400: Unable to initialize new resource in engine.  Failed to create BackupVmSession resource.  Error logging to CIS host, not fetching guestOSImage details.  Failed to login to CIS service at 'HTTPS://192.xxx.xx.xxx/rest/com/vmware/cis/session'.  A 'POST' method to CIS service at 'HTTPS://192.xxx.xx.xxx/rest/com/vmware/cis/session' responded with code 400.  Failed to decode error message:  Failed to decode type '*cis.CisApiError' from '': unexpected end of JSON input". ", url: "https://vproxy02.emclab.local:9090/api/v1/BackupVmSessions",

vProxy error in message handling
The message "Error logging to CIS host not fetching guestOSImage details" should be handled as a warning and allow backups to proceed; however, it is being treated as a failure and stops backups from running.

A temporary workaround is to downgrade to vProxy 4.3.0-41.

This issue is expected to be addressed in an upcoming vProxy release. Check https://www.dell.com/support/home/product-support/product/networker-family/drivers for availability.