Frame skipping is because the shutter speed is lower than the reciprocal of the number of frames. For example, if you shoot 30 frames of video, the shutter speed should not be slower than 1/30S.

When the ambient light is insufficient, the camera will reduce the shutter speed and increase the ISO to meet the minimum shutter requirements. However, when the light is too dim to increase ISO, the shutter speed will drop below the reciprocal of the frame number, and then the frame will jump. The key is lighting, so taking a video is completely different from taking a photo. Taking photos can be underexposed, but video needs proper lighting.