i'll need more information, because right now, with 3 player if I change planet I don't have any issue...
Do you have the issue without any mod except dimension-warp ?
Do you use the latest version ?
What mods are you using ?
Does the game freeze when you warp, place harvester, making people desync ?
Do you have an error message or just "player is dropping from game" (or something like that) ?