When I post the following file to the /{FLOW_ID}/assets endpoint, I get an unclear error message, and I'm unable to publish my flow.

{
    "version": "3.1",
    "screens": [
        {
            "id": "WELCOME_SCREEN",
            "layout": {
                "type": "SingleColumnLayout",
                "children": [
                    {
                        "type": "TextHeading",
                        "text": "Hello World"
                    },
                    {
                        "type": "TextBody",
                        "text": "Let's start building things!"
                    },
                    {
                        "type": "Footer",
                        "label": "Complete",
                        "on-click-action": {
                            "name": "complete",
                            "payload": {}
                        }
                    }
                ]
            },
            "title": "Welcome",
            "terminal": true,
            "success": true,
            "data": {}
        }
    ]
}

I get the following error message:

{
    "success": true,
    "validation_errors": [
        {
            "error": "INTERNAL_ERROR",
            "error_type": "FLOW_JSON_ERROR",
            "message": "Flow JSON validation failed due to an internal error. Please try again.",
            "line_start": 0,
            "line_end": 0,
            "column_start": 0,
            "column_end": 0,
            "pointers": [
                {
                    "line_start": 0,
                    "line_end": 0,
                    "column_start": 0,
                    "column_end": 0,
                    "path": ""
                }
            ]
        }
    ]
}

Anyone experienced similar errors and can help me out to resolve my issue?