Cupboard doors separating

I think the manufacturers of the cabinets simply got a bad batch of glue. It happens. Any hard cabinet wood, properly processed is not going to expand or contract that much. If you look at it closely, what you are probably going to find is some kind of white wood that has been covered with a vinyl type material and shrunk to adhere to the wood base. It's very effective, can be cut to make tight clean joints, and is cheap. That's why the manufacturers use it. I would re-glue it with either Titebond II or Gorilla glue and clamp it.