Mirador viewer

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "https://digi.econbiz.de/viewer/api/v1/records/176840707X/manifest/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e91e0873-96eb-4d83-b4cc-e9ecf887ef9d",
      "cw-c0f106b0-d092-4565-b09b-07dc1f805228"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-45b72f58-095f-4f8c-83f8-e8e57fb959ab",
    "manifestId": "https://digi.econbiz.de/viewer/api/v1/records/176840707X/manifest/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c0f106b0-d092-4565-b09b-07dc1f805228",
    "thumbnailNavigationPosition": "far-bottom",
    "canvasIndex": 0,
    "loadedManifest": "https://digi.econbiz.de/viewer/api/v1/records/176840707X/manifest/"
  }
}