S7 Edge or LG connecting is difficult

[zcmm]

 Hi,all
         my device：
              NRF51822
              S110
              SDK:8.1.0
              connect parameter as follow：
                     #define SLAVE_LATENCY                   0 
                     #define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(4000, UNIT_10_MS)  
                    #define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(5000, APP_TIMER_PRESCALER) 
                    #define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(30000, APP_TIMER_PRESCALER)
                    #define MAX_CONN_PARAMS_UPDATE_COUNT    3  

                   #define MAX_CONN_INTERVAL               MSEC_TO_UNITS(40, UNIT_1_25_MS)
                   #define MIN_CONN_INTERVAL               MSEC_TO_UNITS(20, UNIT_1_25_MS)
       In only one bluetooth device environment（Only my device and Phone），
  i use galaxy S4 、Iphone6、Iphone5、Iphone 7、Huawei P8 ，it is very fast and stable

when these phone connnect with my device .

       But when i use these phone as follow,it is very difficult to connect with my device or Connection is not on my device completely.                                    
       Galaxy s7 Edge(Android6.0.1)  Galaxy s5(Android6.0.1)  Sumsung Galaxy J3(2016)(Android 5.1.1)  LG.

How should I solve this problem????

[Hung Bui]

2 seconds advertising interval seems a little bit too long. If you central doesn't have a very aggressive scanning policy (which I guess other phones have) then it's a pretty small chance that the phone catch the advertising packet. I suggest to change to 100ms (for testing) and change to 500ms in your product. 500ms is a quite good balance between current consumption and the latency it takes to get connected.