Proximity beacon onEnter/onExit delay

Hi, currently the onEnter and onExit event is delayed, does not fire instantaneously. Delay can be up to 5 - 10 seconds.

The beacons running on estimote monitoring packets, i could not find the config to change the broadcasting or advertising interval.

Firmware version: 4.14.4
Hardware version: J1.9_B1.1

Any advice on this event delay issue? thanks