command c is not working at the first press

Recently, I got an issue with my clipboard.

When I press command c, the "edit" button in the top menu flashes, so it should indicates it copied what I select. However, the thing that it pasted was what I selected last time, which means it remember what I selected last time but not this time.

For example,

ABCD ABC

ABCD(correct); ABCD (I copied ABC, but it shows ABCD which was my last copy.)

If I press command c twice or more, it will be correct. very inconvenient !

I saw another similar post about this topic which was solved, I tried that way.

It ask me to type "sudo ......" in the terminal app, after entering the password, it told me that the command was not found.

and I also restore defaults in the shortcuts(keyboard) in the system preferences, did not work either.

Please help!!! thanks.