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_00818/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-82824954-d6a0-40b8-bff1-4c20181bd22d",
      "cw-1134350a-4fec-4f15-a677-b16bcd8f8f1f"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-bc0fdaf5-c453-4cff-89d4-46d2e01cc4d6",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_10P_00818/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-1134350a-4fec-4f15-a677-b16bcd8f8f1f",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_10P_00818/manifest.json"
  }
}