Sweet spot

From Memory Alpha, the free Star Trek reference.

The "sweet spot" is a location aboard every starship, as of 2151, approximately halfway between the artificial gravity generator and the bow plate where the gravity cancels out and reverses.

The sweet spot was named by Travis Mayweather, who enjoyed spending time in the area aboard the freighter ECS Horizon and NX class starship Enterprise. (ENT: "Broken Bow", "Horizon")

Since this phenomenon has never been mentioned chronologically after this episode, its impossible to know whether or not it has been corrected in later vessels.