Hard Pitch Up when closing the speed brakes

[Nitsaw]

During my decent I was descending in VS mode at 2500 and I was a bit high on the path so I opened the speed brakes for a bit and when I closed the speed brakes the nose pitch hard up over 6000 feet a minute on the VSI and I cycled VS off then on and VS window had 8500 feet per minute up I had to quick run the VS back down to 2500 a minute down. The autopilot was very slow to respond even when I ran the VS back down I gained a few thousand feet and lost a ton of airspeed.