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_12N_29773/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-da353a49-d27b-47ca-a6cc-138b80c622c0",
      "cw-fac7c5cf-b428-465f-8ec8-3e6c80bc251b"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cf4785e6-a443-4e82-86ed-e0b96d165774",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12N_29773/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-fac7c5cf-b428-465f-8ec8-3e6c80bc251b",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12N_29773/manifest.json"
  }
}