如题，使用no_ui，订阅行情rb2301和m2301合约，合约代码没有问题，然后间歇性的出现“行情订阅失败，找不到合约XXXX”问题。即有时订阅成功，有时订阅失败。尝试了在 main_engine.connect()之后加入了time.sleep(120)，仍偶发性出现失败报错。不加sleep，也会成功。求教各位大佬，这是哪儿的问题，代码就是下边这个。

 event_engine = EventEngine()
    main_engine = MainEngine(event_engine)
    main_engine.add_gateway(CtpGateway)
    cta_engine = main_engine.add_app(CtaStrategyApp)
    main_engine.write_log("主引擎创建成功")

    log_engine = main_engine.get_engine("log")
    event_engine.register(EVENT_CTA_LOG, log_engine.process_log_event)
    main_engine.write_log("注册日志事件监听")

    main_engine.connect(ctp_setting, "CTP")
    main_engine.write_log("连接CTP接口")
    # sleep(60)
    cta_engine.init_engine()
    main_engine.write_log("CTA策略初始化完成")
    cta_engine.init_all_strategies()
    sleep(60)   # Leave enough time to complete strategy initialization
    main_engine.write_log("CTA策略全部初始化")

    cta_engine.start_all_strategies()
    main_engine.write_log("CTA策略全部启动")

看我的帖子https://www.vnpy.com/forum/topic/31088-qiu-xiu-gai-noui-pydai-ma-zai-cha-xun-he-yue-xin-xi-cheng-gong-hou-cai-zhi-xing-ce-lue-chu-shi-hua