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_06476/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-cc6ba39c-a243-4794-a4e0-7ef4ec23c11b",
      "cw-59b1a58e-3a27-414f-8e50-45705cd8695e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-9c49b311-24cf-4f8c-936d-fa77bf5726c5",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_06476/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-59b1a58e-3a27-414f-8e50-45705cd8695e",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_06476/manifest.json"
  }
}