5.4 broke rigidbody.addForce?

The physics for my player worked, but then when i updated to 5.4, the physics went crazy.

Whenever i add force in a direction, anything passed a certain amount causes the flying player to pull up rapidly.

I've tried every possible solution i can think of, no luck. Here's the gist of how i'm applying force in FixedUpdate(). Basically i have a few things that can apply force to the rigidbody they are added together, then i call AddForce. Any ideas? Any guesses why it would pull upwards like this? I noticed they rewrote transform in 5.4, has anyone else seen problems with the new transform?

     Vector3 forceToAdd = Vector3.zero;

     forceToAdd += applySpecialForces();

     forceToAdd += (movement.normalized * (23 + statManager.FlySpeed)) * multiplier * speedAdjust;

        forceToAdd = buffManager.GetAdjustedSpeed(forceToAdd);

     target.AddForce ( forceToAdd, ForceMode.VelocityChange);