hi
i to update a host cluster with sing image, some hosts succeeded , while others gave the following error:
A failure occurred when starting a host compliance check operation on host : Error: system_error Messages: vapi.invalid.result.code<Recv of frame failed with code: 503 Service Unavailable>
and the failed hosts HA state is stuck HA Agent unreachable as below :

Turned off and on cluster HA many times, and did reconfigure host for vsphere HA .
Noting that the vcenter server 8 with the latest update, also the hosts are 8.0:
Please help and Advice.
Najeeb