Sometimes you finish the block but decide
not to use it.
One could rip and re-sew...
But then again. It may be easier to just toss it aside.
You'd hope you'd notice that things seem out of place
before you finish the top.
Some times it's hard to put your finger on just what went wrong.
Maybe no one will notice.
http://barbarabrackman.blogspot.com/2015/10/ouch-one-tiny-mistake.html