[22:52:32] [Server thread/WARN] [FML]: The Lost Cities loaded a new chunk [-6, 25] in dimension 0 (overworld) while populating chunk [-4, 25], causing cascading worldgen lag.
[22:52:32] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.

i have installed this mod on the server Kettle Dev HEAD-0f5ecbf

server characteristics

• CPU: Intel(R) Core(TM) i5-8250
• RAM: 2G

So, How can I fix this problem?

I'm having this issue as well, using 1.15-3.0.2.

For a majority of the games I've played with it at some point within an hour of playing I hit lag and blocks will stop generating and the AI mobs will freeze.

Using these mods as well:
betteranimalsplus-1.15.2-8.2.1....
engineersdecor-1.15.2-1.1.3.jar
More+Mobs+1.15.2.jar
pandoras_creatures-1.15.2-1.0.0.jar
ProjectE-1.15.2-PE1.0.4.jar
Xaeros_Minimap_20.21.0_Forge_1....