Stutter with 2.5" portable drive when plugged after turning on

I have bought a LaCie Rikiki USB 3.0 500GB drive and I’m having suttering with high bit rate movies when drive is connected after turning on WD TV LIVE (meaning cold start up).

I’m using Samsung Oceanic demo, and when I plug the drive before turning on the WD TV Live (that is, WD TV  and USB drive turn on at the same time), it plays OK. But if I plug the drive when the WD is already on, it plays with interruptions. Slow bit rate movies play OK, suggesting that USB speed is slower in that case.

Is there any reason for that? May it be a problem of drive compatibility?

By the way, it happens with different firmware versions and even with two different WD TV models (I have the original WD TV Live and a hardware version 2, the one that shuts down when turning off).

What happens when you  copy the exact same movie to a usb memory stick and try to play it?

It works OK from a pen drive and also from hard drives in a USB docking station, no matter if connection is done with WD TV Live after booting. I’m talking about usual MKV files of several GB.

Only problem is with this Lacie 2.5" USB 3.0 drive, it works OK if WD TV starts up with the drive connected, but somehow USB speed is reduced if drive is connected when WD TV is already on (connection is done with the provided USB 2.0 cable).

It seems clearly a problem of compatibility or maybe this particular drive has some problem, but it works with normal speed when connected to a PC.

I can live with it, I just wanted to know if something similar happened to somebody, but I already done some searches and didn’t find anything like that.