world generation crashes the server side

I have made a mod that adds 3 new biomes to the game, including new kinds of trees.
when one specific biome generates, in 1.12.2 it would say "cascading world gen lag"
the world hangs and you have to turn the game off using task manager before it actually closes.
basically the same that happens when you set randomTickSpeed to 99999, all the mobs and entities get stuck and no blocks drop when mined.
is there anything I can do to make this issue atleast less bad?