Ended up running into this error today . Could not connect a ISO to the vm using Vcenter 6.5. Upgrading the Vmware Tools version made no difference. Went directly to the Host ESXI and was able to make changes.

Unexpected token (END_OBJECT), expected FIELD_NAME: missing property '_type' that is to contain type id (for class java.lang.Exception)
at [Source: java.io.StringReader@4af4ed59; line: 54, column: 9] (through reference chain: com.vmware.vsphere.client.vm.VmConfigSpec["originalConfig"]->com.vmware.vim.binding.vim.vm.ConfigInfo["tools"]->com.vmware.vim.binding.vim.vm.ToolsConfigInfo["lastInstallInfo"]->com.vmware.vim.binding.vim.vm.ToolsConfigInfo$ToolsLastInstallInfo["fault"])