What if you format to NTFS to try? BTW, what's the model of your drive?

Not sure what's happening. Guess you can wait their reply and share to the forum~

I guess you need to send the puzzle to the support guy and let them figure out for you.

No, it doesn't

I think you can upgrade the firmware to try: http://www.tp-link.com/en/faq-107.html But as your model is quite old, but sure if it can be fixed or not

Qos is not as the same as bandwitdth control function. Qos works when all the devices are online and the High priority devices need high bandwitdh so the low priority devices will take less. But if...