The real culprit of frequent USB error message was data cable. I had another HDD cable when I did scan with it there was no USB error and no bad sector. The whole test took considerable time 7 + 1 hours. On Friday it was quite late at night so I did remaining test yesterday(pic 1, pic 2). The speed of HDD just dropped to half(pic 3) in the later part which might be the sign of imminent failure. Would you provide assistance in case there might be need of RMA. Secondly, cable needs to be replaced as it's faulty.