That is what I meant with a micro pause 
The girl moves up and stops for a fraction of a second and then goes down. If the pause is long enough it might need to be scripted as a plateau with no movement to be perfectly in sync.
Unless, you experience this due to decoding lag because you haven’t re-encoded the video to become a video consisting of full frames only (i.e. no partial frames caused by video compression). Frame by frame doesn’t always work well with the original video downloaded from the official studio site, partially due to the compression (requires lots of extra computations) and partially due to the high resolution (each frame consists of more pixels that must be processed when decoding). I always re-encode the video I’m scripting to 2K resolution with only I-frames (i.e. no video compression). This makes stepping frame by frame while scripting fast and smooth without any lag or other issues. You can use ffmpeg from the command line or use FunExpander to accomplish that. Read more in Tips and Tricks section on the right in this post:
https://discuss.eroscripts.com/t/how-to-get-started-with-scripting/2234