The VRChat client stops with an error when an avatar is set up in Unity under the following conditions
This is an event that occurred while I was setting up my avatar, so it may be easier to cause the error.
  1. Turn off all SkinnedMesh tied to Humanoid.
  2. Place the 3D model (FBX) above under the avatar.
  3. Upload the avatar and use the avatar in VRChat.
The moment it finishes loading, VRChat will close and a Unity error window will appear for a moment.
The following statement was left in the Output Log of VRChat.
2023.08.13 17:13:01 Error - System.InvalidOperationException: The TransformStreamHandle cannot be resolved.
Thrown from job: ÍÏÏÏÎÌÏÍÏÏÏÏÏÌÍÌÌÍÌÌÏÍÎ.ÍÏÌÏÏÌÍÍÎÍÌÏÌÌÏÍÏÍÍÏÌÌÍ
This Exception was thrown from a job compiled with Burst, which has limited exception support. Turn off burst (Jobs -> Burst -> Enable Compilation) to inspect full exceptions & stacktraces. In this standalone build configuration burst will now abort the Application.
ÌÍÌÎÏÏÌÌÍÌÌÍÎÌÍÎÏÎÌÍÌÍÌ:ÏÌÏÌÌÌÎÎÎÎÌÌÏÏÌÏÌÌÏÏÎÎÏ(Animator, Boolean)
ÌÍÌÎÏÏÌÌÍÌÌÍÎÌÍÎÏÎÌÍÌÍÌ:ÍÏÏÍÌÎÍÎÍÎÍÎÍÎÎÌÍÎÎÎÌÏÍ()
ÌÍÌÎÏÏÌÌÍÌÌÍÎÌÍÎÏÎÌÍÌÍÌ:ÏÏÏÎÏÍÏÏÌÏÎÍÌÌÍÏÍÍÏÏÌÌÍ(Animator, VRC_AvatarDescriptor, Boolean, Action)
ÌÌÎÏÍÌÏÌÎÍÍÍÌÌÍÍÍÍÌÎÎÍÏ:ÎÌÎÌÎÎÎÏÍÍÎÎÍÎÎÏÏÌÍÌÏÎÌ(GameObject, VRC_AvatarDescriptor, Boolean)
VRC.SDKBase.SetAnimatorBoolDelegate:Invoke(VRCPlayerApi, String, Boolean)
ÍÍÎÎÎÍÌÎÏÌÏÏÏÎÍÌÍÎÍÍÎÎÎ:ÎÍÎÎÎÌÎÏÏÍÌÍÌÌÏÌÌÏÍÍÍÍÍ(GameObject, String, Single, ApiAvatar, Boolean)
ÎÏÌÍÌÍÏÎÌÏÌÌÍÏÎÏÏÍÎÏÏÍÌ:MoveNext()
System.Action`1:Invoke(T)
Cysharp.Threading.Tasks.UniTaskCompletionSourceCore`1:TrySetResult(TResult)
Cysharp.Threading.Tasks.EnumeratorPromise:MoveNext()
Cysharp.Threading.Tasks.Internal.PlayerLoopRunner:RunCore()
System.Action:Invoke()
The bug was reproduced using a different type of 3D model too.