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_12593/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-8e395a65-eab4-4327-873c-b78dc6e2e4c8",
      "cw-10b59c96-ac6f-4c9a-80ca-bc5ca12e3a49"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-94562baa-4cb6-482d-8d89-c51b95a54eb9",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_12593/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-10b59c96-ac6f-4c9a-80ca-bc5ca12e3a49",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_12593/manifest.json"
  }
}