CC2530: the node lost its parent in power saving mode

HI,

In ZSTACK 2.5.1a ,I set a device as a end device, and predefine POWER_SAVING.the function osal_pwrmgr_device(PWRMGR_BATTERY)  is added after joining network successfully,my consumption is about 50 uA，

but i find the distance between the end device and coordinator is short about 3-4 meters, no PA. and the end device loses its parent easily. why?what settings effect it?

thanks!