[main/FATAL] [mixin/]: Mixin prepare for mod multiworld failed preparing EntityMixin in dim.mixins.json: org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException The specified mixin 'dimapi.mixin.EntityMixin' was not found org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException: The specified mixin 'dimapi.mixin.EntityMixin' was not found

running neoforged 1.21.1 server with sinytra connector
have fantasy dependency installed no problem.
this happens with 1.21 download.
the bundle download has a different error:
[main/FATAL] [mixin/]: Mixin apply for mod multiworld failed dim.mixins.json:EntityMixin from mod multiworld -> net.minecraft.world.entity.Entity: org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException Critical injection failure: @Inject annotation on getTeleportTarget could not find any targets matching 'getTeleportTarget' in net/minecraft/world/entity/Entity. No refMap loaded. [INJECT_PREPARE Applicator Phase -> dim.mixins.json:EntityMixin from mod multiworld -> Prepare Injections -> handler$zbc000$multiworld$getTeleportTarget(Lnet/minecraft/server/level/ServerLevel;Lorg/spongepowered/asm/mixin/injection/callback/CallbackInfoReturnable;)V -> Parse -> -> Validate Targets]
org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Critical injection failure: @Inject annotation on getTeleportTarget could not find any targets matching 'getTeleportTarget' in net/minecraft/world/entity/Entity. No refMap loaded. [INJECT_PREPARE Applicator Phase -> dim.mixins.json:EntityMixin from mod multiworld -> Prepare Injections -> handler$zbc000$multiworld$getTeleportTarget(Lnet/minecraft/server/level/ServerLevel;Lorg/spongepowered/asm/mixin/injection/callback/CallbackInfoReturnable;)V -> Parse -> -> Validate Targets]

They both seem to be upset about EntityMixin.
Please help I love this mod, also is there a way to make flat worlds?