I'm not sure if this is a thing in every map, but in the map Jurassic after a certain amount of time a message will appear in the chat saying: "Something strange is happening...". When this message appears the map seems to change a bit as some of the dinosaurs drop lava and tnt, there are also a ton of blocks that spread everywhere leaving behind a sourceblock of lava or a fire. When this happens it causes extreme FPS lag and it drops a lot of frames, I can get over this, but there's quite some people who just can't really play the game anymore as there FPS drops too much. Of course this feature looks quite cool, but it's extremely unnecessary and should be removed in my opinion, as it makes people drop a ton of frames..