ConcurrentModificationException during chunk feature placement

[15:17:55] [DH-World Gen Thread[0]/WARN]: Unexpected issue when generating features for chunk at pos [C[123,65]], error: [Feature placement].
net.minecraft.class_148: Feature placement
    at net.minecraft.class_2794.method_12102(class_2794.java:377) ~[client-intermediary.jar:?]
    at loaderCommon.fabric.com.seibel.distanthorizons.common.wrappers.worldGeneration.step.StepFeatures.generateGroup(StepFeatures.java:81) ~[DistantHorizons-2.1.2-a-1.20.1-forge-fabric.jar:?]

[15:17:55] [DH-World Gen Thread[0]/WARN]: Unexpected issue when generating features for chunk at pos [C[123,65]], error: [Feature placement].
net.minecraft.class_148: Feature placement
    at net.minecraft.class_2794.method_12102(class_2794.java:377) ~[client-intermediary.jar:?]
    at loaderCommon.fabric.com.seibel.distanthorizons.common.wrappers.worldGeneration.step.StepFeatures.generateGroup(StepFeatures.java:81) ~[DistantHorizons-2.1.2-a-1.20.1-forge-fabric.jar:?]