Mirador viewer

SyntaxError: Unexpected token 'E', "Error from"... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token 'E', \"Error from\"... is not valid JSON",
    "id": "https://iiif.participatory-archives.ch/SGV_10P_00967/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-47ccc0d5-392c-4927-9a14-c50b5d6db51f",
      "cw-2545324d-e7d5-43cf-b661-fb86b7061497"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-18e884cf-70a8-43a9-b7fc-86bc1bd8b8f6",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00967/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-2545324d-e7d5-43cf-b661-fb86b7061497",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00967/manifest.json"
  }
}