I'm trying to extract an in-cell-image from google sheets to later paste to a google docs. Using this method I'm getting an error and couldn't find any documentation about this.

function onClick(){
  var app = SpreadsheetApp;
  var sheet = app.getActive().getSheetByName('FILE');
  var image = sheet.getRange('D4').getValue();
  var url = image.getContentUrl()
  Logger.log(url)
}

Exception: Unexpected error while getting the method or property getContentUrl on object SpreadsheetApp.CellImage

I've also tried using this method using DocsServiceApp->

DocsServiceApp.openBySpreadsheetId(spreadsheetId)
  .getSheetByName("Sheet1")
  .getImages();

But this led to a different error:

Exception: Request failed for https://www.googleapis.com returned code 403. Truncated server response: {
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "exportSizeLimitExceeded",
    "message": "This file is too large to be expo... (use muteHttpExceptions option to examine full response)
    at gToM(SpreadsheetAppp:171:25)
    at getImages(SpreadsheetAppp:34:14)

Does anyone know how to fix one of these errors, or a different method for extracting the images from a google sheet?