Bug of Figma Rest Api

Using the rest api, when i am trying to use the endpoint GET/v1/files/:key/nodes and adding as id an instance node with id: I1:7347;1:7206 the endpoint returns null but the specific id is valid inside the document.

If i use the same id on the GET/v1/images/:key the api returns the image file correctly so i assume that there is a bug on the GET/v1/files/:key/nodes endpoint when adding id’s with the following format I1:7347;1:7206

GET/v1/files/:key/nodes Result

"nodes": {
    "I1:7347;1:7206": null

GET/v1/images/:key Result

  "err": null,
  "images": {
    "I1:7347;1:7206": "https://figma-alpha-api.s3.us-west-2.amazonaws.com/images/0bcd34c5-9540-4786-b593-6d3e92ca0c56"