Putting military medals in display case after moving

I have a problem with the military medals, and so far, Google search hasn't yielded a result so I hope any of you can help.

Two of my Sims have completed the military career, have collected all ten medals and displayed them proudly in their house in Del Sol Valley.

Eventually, the house became too small once they decided to have kids, so I had them move to a bigger house. They brought everything along including the display cases and the medals which went into the general household inventory. Once the Sims had settled into their new home, I placed the medals on the floor in front of the display so the Sims could pick them up and transfer them to the display cases. This had worked in Del Sol Valley after the display cases were moved to the upper floor, so I figured this is the way to do it in a new home, too. 

However, it didn't work. The Sims wouldn't pick up the medals. Instead, I got a message telling me that "This item doesn't belong to this Sim". It doesn't make any sense. They were able to display those medals in Del Sol Valley after they moved there from Strangerville. The only difference between that move and the second one was that they hadn't completed the military career yet and hence didn't own all ten medals. 

It doesn't make sense, and like I said, I haven't found a solution yet. Is there any way to fix this? I'd really like them to be able to show off those medals in their new home, too, I mean, they worked really hard to get them.