与Slack Block Kit模态框交互时未收到block_action负载

我正在开发一款处理团队紧急事务的Slack Bot，此前所有配置存储在JSON文件中，现在需要增强其交互性。之前因邮件风暴导致Bot被反复触发，所以先给Bot添加「Snooze」按钮替代终止进程的操作。

已成功调出模态框，UI显示正常，但点击提交后收不到任何payload数据：

• 预期Flask应用会收到包含交互payload的POST请求，但处理多数Slack交互的根路径「/」、关联Slash Command的「/911_snooze」端点均未收到请求
• 界面同时出现警告三角错误（见配图）

以下是模态框的Block Kit配置JSON（由Block Kit Builder生成后手动调整，下拉选项从外部列表程序化生成，Builder未检测到错误）：

{
    "title": {
        "type": "plain_text",
        "text": "911 Snooze Alerts",
        "emoji": true
    },
    "submit": {
        "type": "plain_text",
        "text": "Submit",
        "emoji": true
    },
    "type": "modal",
    "callback_id": "snooze_911_alerts",
    "close": {
        "type": "plain_text",
        "text": "Cancel",
        "emoji": true
    },
    "blocks": [
        {
            "type": "divider"
        },
        {
            "type": "section",
            "text": {
                "type": "mrkdwn",
                "text": "Application to Snooze"
            },
            "accessory": {
                "type": "static_select",
                "placeholder": {
                    "type": "plain_text",
                    "text": "Application",
                    "emoji": true
                },
                "options": [
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "APP1",
                            "emoji": true
                        },
                        "value": "BOE"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "APP2",
                            "emoji": true
                        },
                        "value": "IBOE"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "APP3",
                            "emoji": true
                        },
                        "value": "GBOE"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "APP4",
                            "emoji": true
                        },
                        "value": "Swift"
                    }
                ],
                "action_id": "application_select_action"
            }
        },
        {
            "type": "section",
            "text": {
                "type": "mrkdwn",
                "text": "How long do you want to snooze for:"
            },
            "accessory": {
                "type": "radio_buttons",
                "options": [
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "5 minutes",
                            "emoji": true
                        },
                        "value": "minutes-5"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "30 minutes",
                            "emoji": true
                        },
                        "value": "minutes-30"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "60 minutes",
                            "emoji": true
                        },
                        "value": "minutes-60"
                    },
                    {
                        "text": {
                            "type": "plain_text",
                            "text": "90 minutes",
                            "emoji": true
                        },
                        "value": "minutes-90"
                    }
                ],
                "action_id": "radio_buttons-action"
            }
        }
    ]
}

内容的提问来源于stack exchange，提问作者Timothy Grant