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_05234/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-650056de-60fa-479e-982f-e1b88d4fe7d4",
      "cw-4194295c-c058-4a50-b806-060b6f81bedc"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-3cb6cac2-d412-47dc-9354-25b36025b3e2",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_05234/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-4194295c-c058-4a50-b806-060b6f81bedc",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_05234/manifest.json"
  }
}