Assuming 5V, 8.7A is ridiculously high!
I don’t know much about the dock (as I’ve been unable to get mine to actually charge my remote at all! 
) but, from what I’ve read I think what you’re experiencing is the over-current protection that was added to the dock firmware a few months ago.
The adjustment to the over-current protection for the Unfolded Circle Dock 3 was included in Firmware Release 0.8.0, which increased the overcurrent limitation to 2000mA.
Unless I missed it, you didn’t mention if you’ve tried a different (reputable) charger and are using the supplied cable? I’d definitely try that. If you’re still experiencing the issue, I’d say, your dock is defective (welcome to the club!)