Program: 11902
Project: 11902
Buggy source:
public static OfflinePlayer generatePlayer(String name,UUID id){
  World defaultWorld=Trident.getServer().getWorlds().iterator().next();
  Location spawnLocation=defaultWorld.getSpawnLocation();
  CompoundTagBuilder<NBTBuilder> builder=TridentFactory.createNbtBuilder("String_Node_Str");
  builder.stringTag("String_Node_Str",String.valueOf(counter.get() + 1));
  builder.longTag("String_Node_Str",id.getMostSignificantBits());
  builder.longTag("String_Node_Str",id.getLeastSignificantBits());
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> pos=builder.beginListTag("String_Node_Str",TagType.INT);
  pos.tag(new IntTag("String_Node_Str").setValue((int)spawnLocation.getX()));
  pos.tag(new IntTag("String_Node_Str").setValue((int)spawnLocation.getY()));
  pos.tag(new IntTag("String_Node_Str").setValue((int)spawnLocation.getZ()));
  builder=pos.endListTag();
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> motion=builder.beginListTag("String_Node_Str",TagType.INT);
  motion.tag(new IntTag("String_Node_Str").setValue(0));
  motion.tag(new IntTag("String_Node_Str").setValue(0));
  motion.tag(new IntTag("String_Node_Str").setValue(0));
  builder=motion.endListTag();
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> rotation=builder.beginListTag("String_Node_Str",TagType.INT);
  rotation.tag(new IntTag("String_Node_Str").setValue(0));
  rotation.tag(new IntTag("String_Node_Str").setValue(0));
  builder=rotation.endListTag();
  builder.floatTag("String_Node_Str",0);
  builder.shortTag("String_Node_Str",(short)0);
  builder.shortTag("String_Node_Str",(short)0);
  builder.byteTag("String_Node_Str",(byte)1);
  builder.byteTag("String_Node_Str",(byte)0);
  builder.stringTag("String_Node_Str","String_Node_Str");
  builder.byteTag("String_Node_Str",(byte)0);
  builder.byteTag("String_Node_Str",(byte)0);
  builder.intTag("String_Node_Str",Dimension.OVERWORLD.toByte());
  builder.intTag("String_Node_Str",GameMode.SURVIVAL.toByte());
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",20);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.listTag(new ListTag("String_Node_Str",TagType.COMPOUND));
  builder.listTag(new ListTag("String_Node_Str",TagType.COMPOUND));
  builder.compoundTag(NBTSerializer.serialize(new PlayerAbilities(),"String_Node_Str"));
  OfflinePlayer generatedPlayer=new OfflinePlayer(builder.endCompoundTag().build(),(TridentWorld)defaultWorld);
  generatedPlayer.name=name;
  return generatedPlayer;
}

Fixed version (ground truth):
public static CompoundTag generatePlayer(String name,UUID id){
  World defaultWorld=Trident.getServer().getWorlds().iterator().next();
  Location spawnLocation=defaultWorld.getSpawnLocation();
  CompoundTagBuilder<NBTBuilder> builder=TridentFactory.createNbtBuilder("String_Node_Str");
  builder.stringTag("String_Node_Str",String.valueOf(counter.incrementAndGet()));
  builder.longTag("String_Node_Str",id.getMostSignificantBits());
  builder.longTag("String_Node_Str",id.getLeastSignificantBits());
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> pos=builder.beginListTag("String_Node_Str",TagType.INT);
  pos.tag((int)spawnLocation.getX());
  pos.tag((int)spawnLocation.getY());
  pos.tag((int)spawnLocation.getZ());
  builder=pos.endListTag();
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> motion=builder.beginListTag("String_Node_Str",TagType.INT);
  motion.tag(0);
  motion.tag(0);
  motion.tag(0);
  builder=motion.endListTag();
  ListTagBuilder<CompoundTagBuilder<NBTBuilder>> rotation=builder.beginListTag("String_Node_Str",TagType.INT);
  rotation.tag(0);
  rotation.tag(0);
  builder=rotation.endListTag();
  builder.floatTag("String_Node_Str",0);
  builder.shortTag("String_Node_Str",(short)0);
  builder.shortTag("String_Node_Str",(short)0);
  builder.byteTag("String_Node_Str",(byte)1);
  builder.byteTag("String_Node_Str",(byte)0);
  builder.intTag("String_Node_Str",Dimension.OVERWORLD.toByte());
  builder.intTag("String_Node_Str",900);
  builder.stringTag("String_Node_Str","String_Node_Str");
  builder.byteTag("String_Node_Str",(byte)0);
  builder.byteTag("String_Node_Str",(byte)0);
  builder.compoundTag(new CompoundTag("String_Node_Str"));
  builder.intTag("String_Node_Str",Dimension.OVERWORLD.toByte());
  builder.intTag("String_Node_Str",GameMode.SURVIVAL.toByte());
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",20);
  builder.floatTag("String_Node_Str",0F);
  builder.floatTag("String_Node_Str",0F);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.intTag("String_Node_Str",0);
  builder.listTag(new ListTag("String_Node_Str",TagType.COMPOUND));
  builder.listTag(new ListTag("String_Node_Str",TagType.COMPOUND));
  builder.intTag("String_Node_Str",0);
  builder.compoundTag(NBTSerializer.serialize(new PlayerAbilities(),"String_Node_Str"));
  return builder.endCompoundTag().build();
}