Well, I don't know, I did read the SMART report several times when I ran HDDScan, and there was no pending allocation. Everything was ok. I saved these reports, and I have them with me.
The bad sector appeared suddenly after I filled the drive with data, and I ran MHDD. This was the first time I wrote data on this drive. Until then, it was only formatted
Yes, I powered this drive at the same time with the other one. In fact, after I filled the other one with data, I copied that data to this one.
I have ran Samsung's ESTOOL, and indeed it detects the problem: it reports 6 consecutive bad LBAs. It prompts me to ERASE the drive, and in case the error persists, contact Samsung.
So, isn't a bad block enough to return the drive? This one is less than 2 months old!!