This is interesting. At least from a troubleshooting standpoint. I tried the same 2 families in Bridgeport and SV2. Both were newly made just for the city. Both displayed the problem in SV2 but not Bridgeport. I should have saved the games.
It could be a mood bug of some sort. I remember the mood would never get to the green for more than a sec, and just plummet upon leaving the house.
I tried something a few minutes ago: I deleted the extracted savegame, downloaded a new copy and extracted it. Upon loading the city, I now get a "Missing Items were replaced" error (Fast Lane is all I am missing if it matters). However, after 30 minutes of playing, I was not able to reproduce the mood problem. I moved one of the same families into the same trailer looking home, and no mood issue. I will keep it running when I can later to see what happens.
In my inexpert opinion, this is probably not a problem with your city. Especially since I seem to be alone in the problem. I appreciate you hearing me out.
Edit: I am even more sure it is the bed bug you mentioned. I found a tread on the official site, and it mentions the sims mood always saying Uncomfortable. Which they were. Why I saw it for the first time in SV2 - who knows.