A new pose added to an animation may change the way the spline curve connecting the keyframes is drawn. It should be limited to one keyframe though.

You may want to load the pose and then go in to the keyframe editor , and check body and Hip , and delete any positioning that isnt what you want. Once those parameter  keyframes are deleted the resr of the animation should fall into place.

Someone else had a problem and they reversed the order , load the last pose , then work back to the start of the animation.