Symptoms:

• In vSAN Skyline Health, an alarm is displayed similar to:
  
  vSAN build recommendation
  vSAN build recommendation engine health
  Unexpected VMware Update Manager (VUM) baseline creation failure. Please check vSAN and VUM logs for details.
   
• Logging in to the Customer Connect Portal is successful.
• Network connectivity to https://partnerweb.vmware.com/service/vsan/vsan-releases.json is working.
  
  For example:
  
  root@infprdv-vc202 [ /tmp ]# curl -v https://partnerweb.vmware.com/service/vsan/vsan-releases.json
  *   Trying xxx.xxx.x.x...
  * TCP_NODELAY set
  ...
  > User-Agent: curl/7.58.0
  > Accept: */*
   
• In the /var/log/vmware/vsan-health/vmware-vsan-health-service.log file, you see entries similar to:
  
  2018-09-28T13:17:44.274Z INFO vsan-health[Thread-43] [VsanClusterHealthSystemImpl::GetClusterHclInfo] includeUpdateItems = False
  2018-09-28T13:17:44.274Z INFO vsan-health[Thread-43] [VsanVumConnection::RemediateVsanClusterInVum] drivers = []
  2018-09-28T13:17:44.274Z INFO vsan-health[Thread-43] [VsanVumConnection::RemediateVsanClusterInVum] build = {u'release': {u'baselineName': u'VMware ESXi 6.5.0 U2 (build 8294253)', u'isoDisplayName': u'VMware ESXi Release  6.5.0, Build 82
  94253', u'bldnum': 8294253, u'vcVersion': [u'6.5.0'], u'patchids': [u'ESXi650-Update02'], u'patchDisplayName': u'VMware ESXi 6.5.0 U2 (vSAN 6.6.1 Update 2, build 8294253)'}}
  2018-09-28T13:17:44.595Z INFO vsan-health[Thread-43] [VsanVumConnection::_LookupPatchBaseline] Looking up baseline for patch VMware ESXi 6.5.0 U2 (vSAN 6.6.1 Update 2, build 8294253) (keys: [291], hash: None)...
  2018-09-28T13:17:44.614Z INFO vsan-health[Thread-43] [VsanVumConnection::CreateBaselineFromOfficialPatches] Update keys stayed the same
  2018-09-28T13:17:44.626Z INFO vsan-health[Thread-43] [VsanVumConnection::CreateClusterBaselineGroup] Creating baseline group (integrity.BaselineGroupManager.BaselineGroupSpec) {
     dynamicType = <unset>,
     dynamicProperty = (vmodl.DynamicProperty) [],
     name = "vSAN Cluster 'vSAN Cluster'",
     description = u'ESXi 6.7 is not recommended because some hosts in this cluster cannot use vCenter 6.5.0 to upgrade to release ESXi 6.7.\n\nNo driver upgrade/update is involved in this case.\n\nLast updated at 2018-09-28 13:17:44 UTC.'
  ,
     targetType = 'HOST',
     baseline = (int) [
        6
     ],
     owner = 'com.vmware.vsan',
     ownerdata = u'ClusterComputeResource:domain-c7945'
  }
  2018-09-28T13:17:44.635Z ERROR vsan-health[Thread-43] [VsanVumConnection::RemediateAllClusters] Failed to remediate cluster 'vim.ClusterComputeResource:domain-c7945'
  Traceback (most recent call last):
    File "/usr/lib/vmware-vpx/vsan-health/pyMoVsan/VsanVumConnection.py", line 1065, in RemediateAllClusters
      performScan = performScan)
    File "/usr/lib/vmware-vpx/vsan-health/pyMoVsan/VsanVumConnection.py", line 893, in RemediateVsanClusterInVum
      desc = desc, patchOnly = patchOnly)
    File "/usr/lib/vmware-vpx/vsan-health/pyMoVsan/VsanVumConnection.py", line 597, in CreateClusterBaselineGroup
      res = bgm.CreateBaselineGroup(spec = spec)
    File "/usr/lib/vmware-vpx/pyJack/pyVmomi/VmomiSupport.py", line 557, in <lambda>
      self.f(*(self.args + (obj,) + args), **kwargs)
    File "/usr/lib/vmware-vpx/pyJack/pyVmomi/VmomiSupport.py", line 363, in _InvokeMethod
      return self._stub.InvokeMethod(self, info, args)
    File "/usr/lib/vmware-vpx/pyJack/pyVmomi/SoapAdapter.py", line 1338, in InvokeMethod
      raise obj # pylint: disable-msg=E0702
  vim.fault.AlreadyExists: (vim.fault.AlreadyExists) {
     dynamicType = <unset>,
     dynamicProperty = (vmodl.DynamicProperty) [],
     msg = "The specified key, name, or identifier 'vSAN Cluster 'vSAN Cluster'' already exists.",
     faultCause = <unset>,
     faultMessage = (vmodl.LocalizableMessage) [],
     name = "vSAN Cluster 'vSAN Cluster'"
  }
  2018-09-28T13:17:44.635Z INFO vsan-health[Thread-43] [VsanVumSystemUtil::AddConfigIssue] Add config issue createBaselineFailed
  
  Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

VMware vSAN 6.x

This issue occurs due to a corruption in the Update Manager database causing this check to fail.

This issue is resolved in ESXi670-201901001 available at Patch Download

Workaround:
To workaround this issue, you can reset the Update Manager database on vCenter. Please follow the documentation outlined in KB article "Resetting VMware Update Manager Database in vCenter Server Appliance 6.5/6.7/7.0" for further instructions.

Note: This above procedure will remove the vSAN default baselines. These baselines are recreated automatically when there is a configuration change to vSAN such as add/remove a host/disk or an update to the HCL DB. You can still safely update a vSAN cluster without the vSAN default baselines.