Thanks for your quick answers,

The HDD is a 2,5″ Seagate “Momentus 5400.6”, 500 GB that was in a “Freecom HDD” portable HDD.
The USB Drive are ScanDisk “Cruzer Fit” 64GB & “Ultra Fit” 128 GB.

I’ve tried to put some soft material under the HDD, I though it helps but it seems that it’s more depending about how the disk starts the record, very different from a take to another. If the record don’t dropout, you’d better not to stop it. But if it drops, it will drop a lot of times all along the record.

When I though about resonance in the HDD, I tried to use the flash memory USB Disk but it was worse.

Best regards,