@Lazslx Go to Edit Town, evict the household, enter the house in Build/Buy, and delete all of the beds. Then save the house to the library (but not the sims), bulldoze the lot, and put the house back. You can go in and add new beds before or after you put the sims back in their house. Once you do this, let the game clock run for a few sim-minutes, then use "save as" to rename the save (so the original remains intact), quit, and reload.
When you place the new beds, I'd recommend putting them in a different room, at least at first. It's always possible something's wrong with the bedroom itself.
Both before you do the above and after (when you quit but before reloading), please delete the five cache files in your Sims 3 folder in Documents\Electronic Arts. For reference, they are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package