vSphere HA agent on host cannot reach some of the management network addresses of other hosts and thus HA may not able to restart VMs if a host failure occurs

May be genuine connection error, so check this using:

vmkping

between the hosts

If this is all fine, it may be just a leftover from a previous issue, which is now resolved. The error may go if you restart the management services on the affected host using:

services.sh restart