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_01175/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-f8e31b13-3f26-4970-8dd2-4bb7a2fb5380",
      "cw-a358f42e-18c2-4e8c-b78b-fc2bce21615e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-ca965db6-5144-447a-a707-f9e912e0a585",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_01175/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a358f42e-18c2-4e8c-b78b-fc2bce21615e",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_01175/manifest.json"
  }
}