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_12P_06481/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-175d5ad0-9bdb-42e3-9e79-6415df6a4f9a",
      "cw-ee48c590-4bb9-4a8b-be6d-97515c66792c"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-e3c5d8ab-3ad2-4932-a96f-2987c5aa5a97",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_06481/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-ee48c590-4bb9-4a8b-be6d-97515c66792c",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_06481/manifest.json"
  }
}