A couple of notes about this particular game and my style. I'm working on my immortal dynasty (my 3rd Gen. is pregnant) and I have 5 sims in play right now. I don't have a lot of extra beds in my house, although I can easily afford more (which is probably the real solution to my issue). I find it easier for my game play, when I have to control so many sims, to essentially assign my sims to a bed.
On to the issue at hand. I have one sim that has developed a desire to argue with everyone, so she's making enemies quickly. Then she's sleeping in everyone else's beds while I'm working with the other sims. As a side note, this sim is my Gen. 1 immortal and I've allowed her a lot of free-will while I'm working on the other generations.
Anyway, from what I've recently observed, my sims appear to not want to sleep in a bed where an enemy once slept. Therefore, I have to reroute the others or do some juggling in order to get everyone to sleep.
I have been successfully using the eyedropper tool in the build menu to copy the bed and replace it. It is just an annoyance.