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_01690/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-87616b8f-cf37-4d49-aeab-56d50e1435c2",
      "cw-7a33193a-83d5-4e60-8c4d-51f5607117d8"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-200a66fa-b261-421c-b544-3ab18eecb85e",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_01690/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7a33193a-83d5-4e60-8c4d-51f5607117d8",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_01690/manifest.json"
  }
}