Large mesh shadows cause lag/jitter movement

So I’m making a space game with planets and the planets are large meshes the performances is good until you go to the night side of the planet. It seems on the night side the grams don’t drop but if another player is walking around you will notice they become very jittery but if shadows are turned off the jitter stops. Obviously having no shadows would look bad sense every thing is lit up at night. All my lighting is dynamic sense the sun is moving so is they a way to make large objects shadows cause less lag/jitter