Vtuber model errors that are bricking Live2d

YoshinoArt

I rigged a vtuber model back in 2023 and everything was fine, but recently after adding some new features and toggles I suddendly noticed that live2d takes MUCH longer to copypaste things and to save the model.
I have a pretty strong pc and models much heavier than this, take a fraction of the time to save (2 minutes compared to 20), so i checked the log tab and found these errors, but i can't understand what they are.

[INFO ] ======================================================================
[INFO ] ======================================================================
[INFO ]
[INFO ] Live2D Cubism Editor ver5.1.03 [ 501030000 / 2024/10/24]
[INFO ]
[INFO ] ======================================================================
[INFO ] ======================================================================
[INFO ] Tue Jun 10 09:32:30 CEST 2025
[INFO ] BASE : jar:file:/C:/Program%20Files/Live2D%20Cubism%205.1/app/lib/Live2D_Cubism.jar!/res/ @IRes_Design
[INFO ] java2d graphics pipeline[ sun.java2d.opengl = NotSet ]
[INFO ] java2d graphics pipeline[ sun.java2d.d3d = false ]
[INFO ] java2d graphics pipeline[ sun.java2d.noddraw = NotSet ]
[INFO ] java2d graphics pipeline[ sun.java2d.metal = NotSet ]
[INFO ] application ui scale : 125.00%
@CubismAppBackupManager
[INFO ] ---------- OpenGL Environment ----------
[INFO ] Version : 4.6.0 NVIDIA 572.83
[INFO ] Vendor : NVIDIA Corporation
[INFO ] Renderer : NVIDIA GeForce RTX 4090/PCIe/SSE2

@CubismParam
[ERROR] exception in custom serializer() of deformerSourceSet : CDeformerSourceSet = com.live2d.cubism.doc.model.deformer.CDeformerSourceSet@7c8fee9f
[ERROR] serializer : public void com.live2d.cubism.doc.model.deformer.CDeformerSourceSet.serialize(org.jdom.Element,com.live2d.serialize.XmlWriter)
[ERROR] element path : CDeformerSourceSet => CModelSource.deformerSourceSet
[ERROR] java.lang.reflect.InvocationTargetException
[ERROR] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
[ERROR] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
[ERROR] at java.base/java.lang.reflect.Method.invoke(Unknown Source)
[ERROR] at com.live2d.serialize.impl.CustomClassSerializer.createElement(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.createElementFromObject(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.writeObject(Unknown Source)
[ERROR] at com.live2d.cubism.doc.model.CModelSource.serialize(Unknown Source)
[ERROR] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
[ERROR] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
[ERROR] at java.base/java.lang.reflect.Method.invoke(Unknown Source)
[ERROR] at com.live2d.serialize.impl.CustomClassSerializer.createElement(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.createElementFromObject(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.writeRootElement(Unknown Source)
[ERROR] at com.live2d.serialize.UUSerialize.serializeToDoc_exe(Unknown Source)
[ERROR] at com.live2d.serialize.UUSerialize.serialize_exe(Unknown Source)
[ERROR] at com.live2d.serialize.UUSerialize.serializeToFile(Unknown Source)
[ERROR] at com.live2d.serialize.UUSerialize.serializeToFile$default(Unknown Source)
[ERROR] at com.live2d.cubism.util.a.h(Unknown Source)
[ERROR] at com.live2d.cubism.util.c.run(Unknown Source)
[ERROR] Caused by: java.util.ConcurrentModificationException
[ERROR] at java.base/java.util.ArrayList$Itr.checkForComodification(Unknown Source)
[ERROR] at java.base/java.util.ArrayList$Itr.next(Unknown Source)
[ERROR] at com.live2d.serialize.impl.SimpleSerializer$AbstractListSerializer.createElement(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.createElementFromObject(Unknown Source)
[ERROR] at com.live2d.serialize.XmlWriter.writeObject(Unknown Source)
[ERROR] at com.live2d.cubism.doc.model.deformer.CDeformerSourceSet.serialize(Unknown Source)
[ERROR] ... 21 more

Katomon

This is just lag of problems on your model and the lack of optimization in your end (adding multiple(more than 6) PSD and stuff like taht will lag how much the model works with, Im already used with working with really laggy models when they have like 5+ outifts ahhahaah sadly it is something you need to get used to it ;w;

YoshinoArt

I was weirded out because this model file is much smaller than other new ones that run smoother?! These are the statistics of the current model that's giving problems "KiraP" and one that works just fine "Chonky".

The only number that is higher in kira is the interps on deformers i'mma try lower that and hopefully it works

YoshinoArt

I solved the problem! Turns out i had a deformer for the upper arm that worked to adjust depending on the arm toggles. I just needed to split it in multiple deformers, one per arm toggle, to drastically reduce the interpolations in deformers number.