I'm the author of Dungeons, Dragons and Space Shuttles 1+2, and I added Avaritia Universal to the pack for version 1.16.5. The Community and I had a bunch of crashes with the issue described above.
at net.minecraft.class_4970$class_4971.handler$zhg000$freecam$onGetCollisionShape(class_4970.java:1077) at net.minecraft.class_4970$class_4971.method_26194(class_4970 ...