DragonFlyBSD

My USB 3.0 stick (fat32 formatted) works great on other Windows / Linux and OpenBSD operating systems. On the stable DragonFly (and after that on "DragonFly-x86_64-20150601-DEV-v4.1.0.1545"-image, I get the usual message instantly after putting it into one of my USB 2.0 ports (of my ThinkPad X200s):

1. umass0: <vendor 0x13fe Patriot Memory, class 0/0, rev 2.10/1.00, addr 2> on usbus3
2. disk scheduler: set policy of da8 to noop

now I have to wait a few seconds and get the rest of the usual messages:

1. da8 at umass-sim0 bus 0 target 0 lun 0
2. da8: < Patriot Memory PMAP> Removable Direct Access SCSI-6 device
3. da8: 40.000MB/s transfers
4. da8: 30176MB (61800448 512 byte sectors: 255H 63S/T 3846C)

after a few seconds more I get the final message:

1. da8: reading primary partition table: error accessing offset 000000000000 for 512
   which prevents me from mounting/using the stick.

Other (USB 2.0 sticks) working great instead.

I've attached dmesg and pciconf -lv output. Please let me know I I could provide any more details.

Over IRC I got a hint that it could be "an unfortunate collaboration of the usb stack and our cam", which could probably helpful.

Thanks in advance for any help.