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_02287/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-cc60a8d7-0142-47fe-8da3-54deaa0db59f",
      "cw-6a7c74ed-88db-4a37-b58d-e277d4de6182"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-08a08aba-3513-4dc3-8b97-ce72bc69b8c2",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_02287/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6a7c74ed-88db-4a37-b58d-e277d4de6182",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_02287/manifest.json"
  }
}