marker 数量超过 18 @markertap @callouttap 就失效了

//添加marker
getStationList() {

            let token = uni.getStorageSync('token');  
            uni.request({  
                url: this.murl + '/screenDevice/selectDevice', //请求接口    
                method: 'GET',  
                sslVerify: false,  
                data: {  
                    type: '125'  
                },  
                header: {  
                    'Authorization': 'Bearer ' + token,  
                },  
                success: (res) => {  
                    console.log(res.data);  
                    this.marks = []  
                    this.mapContext.removeMarkers()  
                    let list = res.data.data  
                    this.ponits = list  
                    let newmarkers = []  
                    console.log(list)  
                    for (var i = 0; i <20; i++) {  

                        let marker = {  
                            latitude: list[i].lat, //纬度  
                            longitude: list[i].lon, //经度  
                            iconPath: '../../static/image/location.png',  
                            width: 20,  
                            height: 20,  
                            station_name: '',  
                            id: i+1,  
                            callout: {  
                                color: '#FFFFFF', // 文本颜色  
                                bgColor: '#FF8C00', // 背景色  
                                display: "ALWAYS", // 'BYCLICK':点击显示; 'ALWAYS':常显  
                                fontSize: 13,  
                                textAlign: 'center', // 文本对齐方式。有效值: left, right, center  
                                padding: 5, // 文本边缘留白  
                                borderRadius: 5,  
                                content: list[i].label,  
                            }  
                        }  
                        newmarkers.push(marker)  
                    }  
                    this.marks = newmarkers  
                    console.log(this.marks)  
                },  

            });  
        },