So, in the end I had to uninstall and reinstall the game. I did this partially using the CCleaner program, partially manually. Today I have tested the game, first without anything extra (apart from all of the EPs and SPs), then with the Store stuff that I have. And it seems, that Ea messed up the age category of some of the base game items.
Since I have no CC, not even mods, in my game at the moment, they can’t be interfering with the game’s content. Still the high-heel pumps in the teenage category break the ankles of the Sim. They didn’t do that before Generations, but have been doing it after the EP. Before the reinstallation of the game I thought that it is some CC that is doing that, but now I know it can’t be. I wonder if it’s an EA bug also that some of the hairs are wrongly categorized, as well as the base game jeans?