HOW2REPRODUCE: If you have one avatar in a project, then import a new FBX for a 2nda vatar, then try to upload the 2nd avatar (doesn't matter same ID or different ID) it will break.

Sometimes what it does is, the 2nd avatar will show the first avatar's info in the control panel, even when you have detached the ID from the 2nd avatar.

Sometimes the "Review any alerts" drop down just breaks, and you cant see what's in there, and you can't upload. If you try it just says the following:

"Avatar validation failed

UnityEngine.Logger:Log (UnityEngine.LogType,object,UnityEngine.Object)

(wrapper dynamic-method) UnityEngine.Debug:UnityEngine.Debug.LogError_Patch1 (object,UnityEngine.Object)

VRC.Core.Logger:LogError (string,string,UnityEngine.Object)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<BuildError>d__150:MoveNext () (at ./Packages/com.vrchat.avatars/Editor/VRCSDK/SDK3A/VRCSdkControlPanelAvatarBuilder.cs:3140)

System.Runtime.CompilerServices.AsyncVoidMethodBuilder:Start<VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<BuildError>d__150> (VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<BuildError>d__150&)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder:BuildError (object,string)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<HandleBuildError>d__142:MoveNext () (at ./Packages/com.vrchat.avatars/Editor/VRCSDK/SDK3A/VRCSdkControlPanelAvatarBuilder.cs:2892)

System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<System.Exception>:Start<VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<HandleBuildError>d__142> (VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<HandleBuildError>d__142&)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder:HandleBuildError (System.Exception)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder/<Build>d__140:MoveNext () (at ./Packages/com.vrchat.avatars/Editor/VRCSDK/SDK3A/VRCSdkControlPanelAvatarBuilder.cs:2777)

UnityEngine.UnitySynchronizationContext:ExecuteTasks ()

"

I documented it in the leaders discord as well: https://discordapp.com/channels/1280940012455723040/1280943382935633992/1394031739596308660

It is fixed by doing nothing, closing unity, and reopening it. It will now display the correct blueprint stuff in the control panel. :(