EA store content is not considered custom content. But, not everything on the official Sims 3 site follows this criteria. There might be some items on the Exchange that have CC in them. For example, you liked a house on the Exchange and downloaded it. Then you install it normally, without being aware that it contains custom content. When the house was installed, the custom content got installed into your game too. If it was created by a starter creator, then it may have some minuses, which can do harm to your game. CC is all the same as mods and hacks. Just the latter change gameplay aspects, while CC changes the appearance of items or creates new items, with new meshes. This is what's done when creating expansion pack items, but those are created by professional game developers. Be sure to uninstall CC and fully delete your caches and test to see if it occurs again.