Help please: family flagged for custom content when uploaded

Wow, I had no idea sim painted art would show up as custom content. Good to know. I did find out what the problem was though, and it was strange. The cat was glitched somehow. I split the family one at a time, and all of them were fine until the cat was added back in. So I had my sim surrender the cat. Then I added a new siamese to the family, named Doc like the last one was. And now the family is uploaded with no custom content warning. That glitched cat was the original EA/Maxis cat, and I had done absolutely nothing to it, not even a new collar. I have no idea how it glitched or when it did. But the problem is solved now, so whew! Happy to know that cc was NOT the problem.

I've never had this problem with Sims, but I had it happen with a house. I don't use CC and never have in Sims 4, so it took me awhile to figure out what was causing it. Turned out it was a painting that my Sim had painted and I'd hung on the wall.
So maybe check all your Sims' inventory?

Well, I'm glad you figured it out. These games have always had random glitches like that unfortunately.