Using Timeline on server drops fps

Hi, everyone.

I created zone circle for battle already placed in map at zero. Calculating random location and next zone size on server and after some delay starts zone shrinking with lerp and timeline running on server. All zone code is running on server so that zone remains same for all clients and also i think zone can control total game play time.

I get decent around 60 fps until zone starts shrinking. As shrinking starts on timeline fps drops to 8-12 fps. and when timeline finished, back to 60 fps.
I also tried with tick using “Tinterp” but same result.

How do i keep my fps steady ?
And also i got term “rubber band effect” on other’s question. is it rubber effect ?