Also, please double-check that you have a valid forward and reverse DNS entry for the system, that NTP is reachable (and synched with the underlying host), and that you have a compliant OVA for your system?
With both systems suffering the same issue, it is reasonable to expect that there is some underlying issue. You said your NTP is accessible by the VMs. Is it synched with the ESXi host? Your error can happen if NTP is not synched to the ESXi host.
Open up a TAC case on this. Before that, enable the serial port on the VM instance and restart the installation. If will fail again but you would should have the logs for RCA through the serial port onto your datastore from where you can download them fo analysis. You can share it here and open up a TAC case as well.
