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_01002/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b0e1ee2b-f908-4d30-9d1a-897dcad918c8",
      "cw-1ec1eaf6-e751-44e2-8988-603205011381"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5e5e41fb-194c-4a10-bfb1-3da2f07fc7f8",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_01002/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-1ec1eaf6-e751-44e2-8988-603205011381",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_01002/manifest.json"
  }
}