There have been several solutions for this type of thing, but start with this one:
http://answers.ea.com/t5/The-Sims-4/Sims-4-I-have-two-mailboxes-and-a-unicorn-that-I-can-t-remove/td-p/4139027
Be sure to read all the posts for the solutions that worked for others.
If none of those work, read the posts on this forum:
http://www.carls-sims-4-guide.com/forum/index.php?topic=23323.0
One post mentions a mod that can be used. I won’t post that link as I’m not sure if it’s appropriate to post mod links. However, it’s from Mod The Sims called “ enable advanced debug/cheat interactions”.
Note it’s an outdated mod, so if you try to use it, read the last couple pages of the comment section first. Although it still works as is for some, others have had to change it slightly to work with the current patches. Some say it’s because of GTW or conflict with other mods, or perhaps “testingcheats true”.
In any case, no matter which solution you may try, be sure to backup your game first before trying any of it just in case something goes wrong.
