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_04P_01175/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-c393b5ae-efbd-469d-a195-ca8ef3dab181",
      "cw-6ff9630a-fa58-471d-bf9e-dbf0886cc512"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-030cc5ac-3be2-4ca5-9e74-6196e3006ee3",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_04P_01175/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6ff9630a-fa58-471d-bf9e-dbf0886cc512",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_04P_01175/manifest.json"
  }
}