Plug [Q] Sudden charging issues.

I just picked up a used TF300T on Craigslist yesterday. It was completely stock, running 4.2.1. When the lady handed it to me to check out, both the dock and tablet were fully charged and everything was functioning normally. It wasn't til later that I tried to charge the tablet/dock that I noticed the dock wasn't taking a charge, but the tablet was charging. Eventually, the dock battery went down to 0% and that's when things got worse. Now, neither the dock nor the tablet will charge. Even when the tablet itself has the cable plugged directly into it, it still won't charge. No matter which port I plug the cable into, my PC recognizes it and mounts internal storage; but the stupid thing won't charge.

I've since unlocked the bootloader, installed the latest TWRP, wiped data/factory reset, rooted, etc. Nothing has made any difference. The fact that everything was fully charged up seems to support the original owner's claims that she never had any issues with it. I just don't understand how it could be fine one minute and suddenly have issues once I take possession of it. I'm pretty anal about caring for my gadgets, so it didn't suffer any bumps or any kind of mishandling in the 24 hours that I've owned it. I'm at a loss. Any ideas?

The only activity I've seen from the dock's charging LED came after the dock was fully discharged. Now, if I have the tablet docked and the charger plugged into the dock, the LED blinks orange. I've never seen the LED do anything without the tablet docked. No idea if that's significant, but thought it was worth mentioning. I did some searching and found that some people had charging issues with their docks, but didn't stumble across anything that seems to match what's happening with mine.
Current Device: Virgin Mobile HTC Evo V
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