I just installed VMware ESXi on a Dell R620 to test with. I have an opensuse 42.3 Linux guest VM that is powered off. When I go to export as OVF I can fetch the .ovf file, but it fails to fetch the associated VMDK. In Google Chrome I get "Failed - Network Error." When I use Firefox it fetches about 80-90MB of the VMDK and then stops. There is no error shown. On the ESXi host, it shows the request for the export but does not log any actual error.
I tried downloading the VMDK via the datastore browser but that didn't fetch the actual vmdk.