inventory won't work!

I've been having similar problems when sims travel, and I have no mods and no cc in my game. My teenage vampire just went to school with a homework book, a kinfe block he had just mad and a dozen plasma packs. Came back with only the homework book, which he had upon creation. Similarly, in another save file, which is a legacy in the fourth generation, three girls (two teenagers and a child) went to school. One of them came back with everything as usual in her inventory, the child came back with the elementary school homework, but lost her completed projects, and the teenager who had aged up during the weekend came back with her elementary school homework, but lost her completed projects and her high school homework...