Drone altitude drop while yawing

Hi all. I need some help with flight log analysis. I am currently using F450, Pixhawk 2.4.8, RPI and Picamera - working on a project that is autonomous in indoor environment.
What i’m doing here is that - I rise to 1m, yaw and then rise to 1.5m and yaw again.
Rise and yawing to 1m seems fine. However, when at 1.5m the drone begun to yaw, there will be a altitude drone and the drone starts to oscillate up and down.

Here is my flight log. https://review.px4.io/plot_app?log=488937ef-a25f-483c-a876-db61dc469fe8

I can’t seem to figure what is happening but I noticed that there is an oscillation at Velocity and Local Position Z.

Please help, and thanks in advance!