Varying conditions with humidity will cause the wood to expand and shrink. What you're most likely seeing is the result of very low humidity. If you live in a part of the country where the conditions are dry a lot or vary, you'll see the floor 'move'. BUT, until you have a change in the humidity, you won't know for sure if the floor is as it is because of humidity or shoddy workmanship.
A good level of humidity in the house is 35-40%, give or take. If you have a humidifier, set it to the low side, and work up to 40. If you can measure the humidity in the house too, this will confirm that your setting is 'working'. As an aside, it's best for an installer to install a hardwood floor when the humidity is at 'normal' levels. Usually, the wood is left in the house for about a week to become 'acclimated' to the home's conditions before it's installed. At worst, see if it's feasible to have a humidifier installed on your plenum.