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_06107/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-d5354087-d71b-4c72-b531-762693b35deb",
      "cw-fd6d89ce-b14b-4ca1-a359-68c6d6b968d1"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-6fe55e37-843b-4c65-98cb-a01615e024b2",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_06107/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-fd6d89ce-b14b-4ca1-a359-68c6d6b968d1",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_06107/manifest.json"
  }
}