Jittering issue in C++ ULFG

[BadrinathS]

I am trying to implement ULFG detector in C++ for a video. Currently the code works and detects face on each frame, but the issue is that the detected box changes its size every frame (person's face in the frame is same size as before) which cases huge problem in facial landmark detection as it relies heavily on face detector box size.
Please see the attached gif and notice on the bounding box size, it changes every frame even though the face size doesn't

Can you help me resolve this?

[BadrinathS]

The bounding box jitters and it would be great if someone can help me out.