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_00995/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-55cf43e4-4fec-48a5-9261-7b5df9d056bd",
      "cw-8f29eb12-19f7-4afb-ba11-c4011559f736"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-55c5eb9b-82a9-4af9-b92e-a3f2956a2892",
    "manifestId": "https://iiif.participatory-archives.ch/SGV_12P_00995/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": true,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8f29eb12-19f7-4afb-ba11-c4011559f736",
    "loadedManifest": "https://iiif.participatory-archives.ch/SGV_12P_00995/manifest.json"
  }
}