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_00724/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-43d11190-3ee7-45f6-be27-e24f900f9add",
      "cw-55cb424c-c582-4698-b4b5-a95c2eb02d5a"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-02697360-1330-4f40-b386-b0407399f29a",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00724/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-55cb424c-c582-4698-b4b5-a95c2eb02d5a",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00724/manifest.json"
  }
}