I bought a 16GB Sandisk Extreme USB 3.0 Flash Drive two weeks ago, and it worked under USB 3.0 mode on the first three or four days. After that, I found the drive can only work under High Speed (USB 2.0) mode even plugged in a USB 3.0 port.
I tested the drive on USB 3.0 ports on my desktop, which are offered by Intel chipset and Asmedia USB 3.0 chip, and on my MacBook Air 2012, but it still worked under USB 2.0 mode.
Meanwhile, my USB 3.0 3.5" external HDD box can work properly under USB 3.0 mode.
In addition, I only plugged one device (a.k.a this drive) directly (i.e. without hub) in both machines, no other device plugged in their USB 3.0 ports.
Beside asking the distributor for replacement, what can I do for that?