FPS issues?

[GracefulUni]

My family built an underground smelting area and it kinda big and whenever you login at the home base or come through a portal back to the house there is some massive lag for about 5ish seconds, I tried testing if it was rare magic portals but that isn't the case. Is it possible that the lag might be due to the mineshafts?

[GracefulUni]

update, after removing mineshafts all the lag is gone, i believe its due to how far and you mine inside these mineshafts and how big theyre especially if multiple are placed around the world, its a massive fps and lag issue when this happens