Transcend JF V60

[Artyom Mirgorodsky]

Hi.
I have a trouble with USB flash Transcend JF V60

umass0: <USBest Technology USB Mass Storage Device, class 0/0, rev 2.00/1.00, addr 2> on uhub2
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <JetFlash TS4GJFV60 0.00> Removable Direct Access SCSI-2 device 
da0: 40.000MB/s transfers
da0: 3935MB (8060927 512 byte sectors: 255H 63S/T 501C)

When I copy big files from flash or execute 
dd if=/dev/da0s1 of=/dev/null bs=1M

process copying hangs. After some time (1-2 minutes), process renews copying and hangs again.
On linux or windows all good.