It sounds like you're using your "stilled seat" either too abruptly or too "loud". Stilled seat is good to downshift, and includes stretching taller, gently curving the lower back, and tightening the abs. The degree of the seat change determines the reaction. Maybe try not stretching so tall, not tightening quite so much, giving a more subtle stilling. See how little you need to change to get a smoother response.
Here's a video that really helped me out with improving transitions. The whole thing is definitely worth a watch, but if you're pressed for time the info on the stilled seat specifically starts around 4:34