Leaves deteriorating

[Lepua]

upon the moment the simulation distance enters the rocky_bumpy_mountains the leaves of the jungle trees just erode.

idk if you can fix it but GL i guess.

[LunaticWyrm467]

I can also confirm this. This causes immense lag.

[Lepua]

I can also confirm this. This causes immense lag.

you could try lowering the simulation distance

and in World edit (if creative world) try
/give @p minecraft:oak_leaves{BlockStateTag:{persistent:"true"}}
use that in game and replace all leaves of a type with those.

never did it myself but it could fix your problem.