I may have found a workaround for this, but I am not sure if this works for everyone:
If you have wrong traits in the relationship panel (this applies to toddler traits on children and older or for the case if you changed traits via cheating (or CAS), try using the "Get to know" interaction several times, until the other sim knows every trait about the sim with the (visibly) wrong traits. But for me, this does not work forever, because, after a while, the relationship panel will show the wrong traits again.
So yeah, it is a workaround, but only temporarily. Hope this helps.
(If your sim isn't married or in a relationship, you can still command an alien to erase the sim's mind, so he / she gets to know the sim from scratch, but this is the rough method if nothing else works).
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