The rainfall reading is not re-zero after 1 hour

[bmkia13]

Hi, i have 3 unit of dfrobot tipping bucket rainfall sensor, https://wiki.dfrobot.com/SKU_SEN0575_Gravity_Rainfall_Sensor, tried both i2c and uart mode using arduino uno. First i pour the water into the bucket, reading recorded successfully but after 1 hour Sensor.getRawData() and Sensor.getRainfall(1) are not return to 0 after 1 hour,
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i follow exactly the code from https://wiki.dfrobot.com/SKU_SEN0575_Gravity_Rainfall_Sensor

library used : 1) https://github.com/DFRobot/DFRobot_RainfallSensor 2) https://github.com/DFRobot/DFRobot_RTU

length of wire from pcb to arduino uno is 40 cm

Any ideal about this? Thanks