Sometimes they sound wrong; sometimes they sound right. Does that about sum it up, so to speak?
I was reading over this sonnet recently reposted as one of a sequence of four. In the third quatrain you will see:
But the Knights of the Copybook Headings
Show… that our apathy caused you to win;
We will never forget that beheadings,
Though… were the wages of this kind of sin.
I had originally changed this third rhyming word because of the identical or same word rhyme. I realised after some time of reflection that it sounded fine the way it had been. Why, I wondered, was that. I believe the answer lies in the odd or feminine lines containing the duplicate word or sound. This understanding opens up possibilities. One has to do some thinking though regarding forms other than ABAB types, wherein the feminine lines are easily understood as such. What about an Italian sonnet?
Hmmmm…. Does this not bear more thinking?