If its new then what probably happened was the home was built during a rainy period which increased the moisture content of the wood. Many builders are simply paper contractors and do not take such things into considerations… they are simply trying to finish the home as quickly as possible.
If its not new then it probably has air infiltration issues which again depending on the humidity.
Either way it would be worth pulling off several receptacle plates and getting readings… especially where the issues are occurring.
Drywall pops are more associated with improper fastening… same thing can be said for siding… trying to get installers to understand the need to hit studs instead of just relying on OSB or Plywood is like talking to a brick wall at times.
Lastly, he may want to also check the fastening of the cabinets.
Many of the box cabinets that builders use today are crap…the facades look great but other than that they are particle board and masonite with very few wood ledgers to nail to.