Smartdrive both quick drive test and complete drive test failed

I have My Book Essentials 2Tb. Why it not able to pass these tests?

firmware version

Lion 10.7.4

If the test failed you need to replace it. 

Frankly, I’d like to get a useful answer. After all, the drive works and passes tests in other programs (although there were some issues with Time Machine).

Well you can also use the disk utility and run a test from there. If the SMART test fails for example, even though you see that the hard drive is working, it will eventually fail.