When I execute the script "(exec -l -a specialname /bin/bash -c 'echo $0' ) 2> error", why it output ^[7^[[r^[[999;999H^[[6n to error

when I do the bash test, the run-builtins fails, after some search, I found that it output ^[7^[[r^[[999;999H^[[6n to the stderr, so I redirect it to a file error. I cat it that it output a blank line, I open it using vim which I found the "^[7^[[r^[[999;999H^[[6n", why?