We are running vSphere 6.5U3 with vCenter Server 6.7U3 on 4 Cisco C240 M4 servers. Running NSX and vSAN.
Last week I wrapped up an issue with VMware Support where I could not add a host back into a NSX VDS. During this time we had DRS turned off. At the end of the day Friday I turned DRS back on once the VDS issue was resolved. This morning I saw the warning "Unable to apply DRS resource settings on host". This occurs twice, there is no other warning attached to these messages. I tried checking the vpxa.log and hostd.log for "failed (saw posts on failures of vmware tools installs) but found nothing. I restarted the vpxa and hostd agents and it cleared up for maybe 10-15 minutes then came back. This only happens on the one host we worked on.
I cannot say the exact reason of why this is happening however please check the /var/log/vmware/vpxd/vpxd.log for the respective time when the alert triggered for the host similar to the KB https://kb.vmware.com/s/article/2013175
Possibly there is a communication issue or config issue between the VC and ESXi host.
I had saw a forum post on checking the scratch location. This hosts scratch location was empty, I know I configured it a month ago before all this happened. I put the location back in and immediately it did not change anything. The next day I looked and the warnings were gone and it has been stable since.
Thanks for the helpful hints!