Xray-core: proxy/vless/outbound: failed to use xtls-rprx-splice, maybe "security" is not "xtls"

This is my first time trying out xray, and i got: app/proxyman/outbound: failed to process outbound traffic > proxy/vless/outbound: failed to use xtls-rprx-splice, maybe "security" is not "xtls"

Route spliting is taken cared by iptables.

{
    "log": {
        "loglevel": "debug"
    },
    "policy": {
        "levels": {
            "0": {
                "statsUserUplink": false,
                "statsUserDownlink": false,
                "bufferSize": 1024
            }
        },
        "system": {
            "statsInboundUplink": false,
            "statsInboundDownlink": false,
            "statsOutboundUplink": false,
            "statsOutboundDownlink": false
        }
    },
    "inbounds": [
        {
            "port": 1080,
            "protocol": "dokodemo-door",
            "settings": {
                "network": "tcp,udp",
                "followRedirect": true
            },
            "streamSetting": {
                "sockopt": {
                    "tcpFastOpen": true,
                    "tproxy": "tproxy"
                }
            }
        },
        {
            "listen": "127.0.0.1",
            "port": 53,
            "protocol": "dokodemo-door",
            "settings": {
                "address": "127.0.0.1",
                "port": 53,
                "network": "tcp,udp",
                "timeout": 0
            },
            "streamSetting": {
                "sockopt": {
                    "tcpFastOpen": true
                }
            }
        }
    ],
    "outbounds": [
        {
            "protocol": "vless",
            "settings": {
                "vnext": [
                    {
                        "address": "mydomain.cc",
                        "port": 1433,
                        "users": [
                            {
                                "flow": "xtls-rprx-splice",
                                "id": "19f853df-0c5d-4e88-9112-c0058f1096e7",
                                "encryption": "none"
                            }
                        ]
                    }
                ]
            },
            "streamSetting": {
                "security": "xtls",
                "xtlsSettings": {
                    "serverName": "mydomain.cc",
                    "certificates": [
                        {
                            "certificateFile": "/etc/xray/mydomain.cc/fullchain.cer",
                            "keyFile": "/etc/xray/mydomain.cc/mydomain.cc.key"
                        }
                    ]
                },
                "sockopt": {
                    "mark": 2,
                    "tcpFastOpen": true
                },
                "tcpSettings": {
                    "header": {
                        "type": "http",
                        "request": {
                            "headers": {
                                "Host": [
                                    "www.bing.com",
                                    "www.kernel.org"
                                ],
                                "User-Agent": [
                                    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36",
                                    "Mozilla/5.0 (Linux; Android 10; Blackberry) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.101 Mobile Safari/537.36"
                                ],
                                "Accept-Encoding": [
                                    "gzip, deflate"
                                ],
                                "Connection": [
                                    "keep-alive"
                                ],
                                "Pragma": "no-cache"
                            }
                        },
                        "response": {
                            "headers": {
                                "Content-Type": [
                                    "application/octet-stream",
                                    "video/mp4"
                                ],
                                "Transfer-Encoding": [
                                    "chunked"
                                ],
                                "Connection": [
                                    "keep-alive"
                                ],
                                "Pragma": "no-cache"
                            }
                        }
                    }
                }
            },
            "mux": {
                "concurrency": -1
            }
        }
    ]
}