It's been that way since it came out. The DLNA committee never mandated that feature so nothing busted. The USB connection is not DLNA and you may see it work much better.
Do we need to cover off the other simple reason that the network connection is 100 or less Mbps and the USB is 400+?
My Twonky 7.0.8 Special was installed inside my NAS, My Book Live 3TB (MBL).
The movies was played(streamed) on my Samsung TV 46C7000 via a router connected to the MBL.
Why the current DLNA functionalities on my Samsung TV such as Fast Forward, Rewind and Last Played screen are unusable with Twonky?
However, if I connect the movies via USB and portable HDD, all the funtions works very well.
Please help me.