Unable to Clone Virtual Machines in the vSphere (HTML5) Client when ESXi host(s) are in Maintenance Mode

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• You are unable to clone a virtual machine to a cluster / resource pool / folder while one or more hosts in this cluster are in maintenance mode, when using the vSphere (HTML5) Client. When doing so, you see the error: "Specify a valid cluster, host, resource pool or vApp as destination."
• You are able to clone a virtual machine in the same state as above, using the vSphere Web (Flex) Client.

Environment

VMware vCenter Server 6.7.x
VMware vCenter Server Appliance 6.7.x
VMware vCenter Server Appliance 6.5.x
VMware vCenter Server 6.5.x

Cause

This is a known issue with all previous versions of the vSphere (HTML5) Client.

Resolution

This issue is resolved with vCenter Server 6.7 Update 3b.

Workaround:
To work around this issue, use the vSphere Web (Flex) Client to clone virtual machines. Alternatively, set DRS to manual and take hosts out of maintenance mode temporarily. Note that the latter is dependent on the reason why those hosts are in maintenance mode.