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_05198/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a016c5a4-7878-4545-82bb-b8c4637e55c2",
      "cw-567e1a00-08f7-4e6e-87f7-56dca33c2efc"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-8a4171b5-3288-46c8-91f6-358864566f0c",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_05198/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-567e1a00-08f7-4e6e-87f7-56dca33c2efc",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_05198/manifest.json"
  }
}