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_12P_06473/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-c2b15a66-485e-4804-a10e-7bcab8d6f818",
      "cw-61fcbd67-e2a3-4bca-9832-9e64c1bceb44"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cdd9057a-40cf-46e8-af6b-f361a2bfdb07",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_06473/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-61fcbd67-e2a3-4bca-9832-9e64c1bceb44",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_06473/manifest.json"
  }
}