There are a lot of possibilities:
- Broken HDD: You can try to use CrystalDiskInfo to check the SMART values.
- Defective USB case: Put the HDD in another case or plug it directly in the mainboard.
- Broken USB cable: Try a different one.
- Driver problems: Update you chipset drivers.
I found that my MFT Zone is in the middle of the hard disk, could it cause this type of crashes ?
Offtopic : This kind of crashes could cause damage to the files that was on the HDD besides the one that was writing at the time?
NTFS is quite resistant against files system corruption but if you've enabled the cache on the USB disk (the default) it's very likely to get corrupted entries because the changes in the file system are not committed to the disk right away.