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_10588/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-1f73769d-2b48-43a2-91af-dfa92e30fe10",
      "cw-0640324d-ed8c-4b4d-9609-f2d7c902ff23"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-d907e8af-ecc9-4955-9abd-0f83351fca63",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_10588/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-0640324d-ed8c-4b4d-9609-f2d7c902ff23",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_10588/manifest.json"
  }
}