I've tested the drive while the week-end: bad results for me
I've tried to image more than 20 disks with SCP and then write them with the SFD-321B. They don't work at all, even the non-protected games were faulty on the real hardware. I firstly thought my floppies were damaged, so I used some new disks. Same results. Then I tried to copy directly the contain of a disk with SCP, w/o imaging it. Same results, the disks weren't copied correctly. Even if the GEM appeared and the desktop.inf was correctly read, the main .PRG can't be launched because of damaged (or missing?) data on the disks.
So, I came back to my old Sony Drive, tried to image same disks with the same floppies and they worked like a charm on my STE.
Maybe the drive is broken, even if it looks like new. Anyway, I'll try with another manufacturer tonight. I need a second drive since the first one (the Sony drive) is already monopolized by KF.