The light on the Dock is an indicator of the Voltage level on the battery within the Dock.
A constant green light indicates that the Charging Dock is charging.
When the voltage level passes a threshold that indicates sufficient charge, the light will Turn OFF.
However when charging, as the voltage fluctuates around the threshold, there might be a blinking pattern. It is to be expected. Although most docks won't flash, some might.
Just to prove the point, watch a Dock charge an Olive without a USB connection. After the battery is drained a bit, we connect the USB cable. The Dock charges on a solid green for a few seconds and then as it approaches the threshold, it starts blinking as expected.
*Note: The video is slightly sped up