Household Sims loose existing relationship

Hi sorry I didn't see this until now and those sims that were having the relationship disappearing issue died but I did have it happen I think at least one more time between two of my sims in the same family, save, and household who are siblings. Would it still be worth it to send the save file?

Also I saw the comment from crinrict theorizing that it might be related to sims aging up to young adults and not getting the prompt to pick a third trait and that did just happen to me in the same save with a grandchild of the two original sims to have their relationship disappear. Is there a fix for that problem? I was just gonna go into CAS and give him a third trait manually but I didn't want to potentially screw up my save so I just exited the game. Also that sim is dating the grocery store delivery girl and they just adopted a cat but I don't know if either of those has anything to do with the issue.