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_00014/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e53e97c9-6838-4830-8b27-29171a4dbdff",
      "cw-6130da6d-9451-4897-b146-4eb3a2ddf014"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cf6373f8-f279-48aa-88b8-d1c89af7ef9f",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00014/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6130da6d-9451-4897-b146-4eb3a2ddf014",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00014/manifest.json"
  }
}