When the server starts the game have no lag, but after some time playing the ping starts to jump to high numbers like 1000ms and then the server just crash and everyone get kicked
It may happen due to: too many particles, parts, script loops etc. To fix the particle or part lag, simply just add a script to it to remove it after a certain amount of time being spawned.
ex : game.Debris:AddItem(PART_NAME,2) --will delete the part in 2 seconds.