The good news is that there is nothing wrong with your sub.
The less good news is that when used in a "wired" configuration, the blue wireless indicator light will continue to blink as the unit tries in vain to sync up with the wireless transmitter that is not in use.
We understand the constantly blinking blue light is annoying, to put it mildly. There are two possible solutions.
1. Go ahead and plug in the transmitter somewhere in the room, even if it is not being used. The Dynamo should "sync" to this and the light should remain a solid blue.
2. You can cover the offending light with a small piece of electrical tape or some other opaque material.