Hi,
So, I was able to solve the problem myself. Actually I was using 'shinycssloaders' library to bring in a busy/loading sign in rshiny.
It was attached to datatable, and the animation I had chosen was a bouncing one. The way the library works is that the animation is always running and when the table is ready, it just outputs on top of the animation.
Since the animation was a bouncing one and it was always running in the background, it was actually making the table and the whole UI to bounce as well, even when it was superimposed by a table. Definitely not desirable behaviour.
I tweaked it by choosing some other loading sign that does not bounce, and this solved my problem.