@olivierlambert It appears that this is in fact an issue with XOCE. I was able to reproduce the same error. I am having no issue with the XOA appliance or XCP-ng Center.

vm.create
{
  "clone": true,
  "existingDisks": {},
  "installation": {
    "method": "cdrom",
    "repository": "54f2aa37-7552-4e36-bb4f-2ae0cf5999c1"
  },
  "name_label": "Windows 10 (64-bit)",
  "template": "68055f83-4afe-2701-51d5-d6ca8fc90a6d-7774689b-4ca1-4dea-8545-dddd6b64c17f",
  "VDIs": [
    {
      "bootable": false,
      "device": "0",
      "size": 34359738368,
      "type": "system",
      "SR": "ef976096-efb6-5a74-bc37-e6d279b08e7d",
      "name_description": "Created by XO",
      "name_label": "Windows 10 (64-bit)_etade"
    }
  ],
  "VIFs": [
    {
      "network": "6061fbef-74bb-945c-ba88-d6868b419817",
      "allowedIpv4Addresses": [],
      "allowedIpv6Addresses": []
    }
  ],
  "CPUs": 2,
  "cpusMax": 2,
  "cpuWeight": null,
  "cpuCap": null,
  "name_description": "",
  "memory": 4294967296,
  "bootAfterCreate": false,
  "copyHostBiosStrings": false,
  "secureBoot": false,
  "share": false,
  "coreOs": false,
  "tags": [],
  "hvmBootFirmware": "uefi"
}
{
  "code": "INTERNAL_ERROR",
  "params": [
    "(Failure \"Expected string, got 'N'\")"
  ],
  "call": {
    "method": "VM.get_power_state",
    "params": [
      null
    ]
  },
  "message": "INTERNAL_ERROR((Failure \"Expected string, got 'N'\"))",
  "name": "XapiError",
  "stack": "XapiError: INTERNAL_ERROR((Failure \"Expected string, got 'N'\"))
    at Function.wrap (/opt/xo/xo-builds/xen-orchestra-202205131525/packages/xen-api/src/_XapiError.js:16:12)
    at /opt/xo/xo-builds/xen-orchestra-202205131525/packages/xen-api/src/transports/json-rpc.js:37:27
    at AsyncResource.runInAsyncScope (node:async_hooks:202:9)
    at cb (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/util.js:355:42)
    at tryCatcher (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/promise.js:547:31)
    at Promise._settlePromise (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/promise.js:604:18)
    at Promise._settlePromise0 (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/promise.js:649:10)
    at Promise._settlePromises (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/promise.js:729:18)
    at _drainQueueStep (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/async.js:93:12)
    at _drainQueue (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/async.js:86:9)
    at Async._drainQueues (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/async.js:102:5)
    at Immediate.Async.drainQueues [as _onImmediate] (/opt/xo/xo-builds/xen-orchestra-202205131525/node_modules/bluebird/js/release/async.js:15:14)
    at processImmediate (node:internal/timers:466:21)
    at process.callbackTrampoline (node:internal/async_hooks:130:17)"
}