Hiyu
When opening up a Unity World Project, and it opens up to a scene that contains/references a 3D texture, and if the VRChat SDK's Builder panel is already open, then it can throw the error shown in the image.
(The 3D texture, in my case, is likely an AgX LUT custom render texture I'm using from Silent's custom tonemapper https://github.com/s-ilent/custom-tonemap/ )
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Repro steps:
  1. In Unity Project, use a shader & material in the scene that references a 3D texture (must be a true 3D texture, not a texture array)
  2. Open the VRChat SDK and leave it at the Builder panel
  3. Close and reopen the Unity Project
  4. See Error thrown in Console (shown below)
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Full error:
Error assigning 3D texture to 2D texture property '_MainTex': Dimensions must match
UnityEngine.Material:GetTexture (int)
VRCSdkControlPanel:GetOversizeTextureImporters (System.Collections.Generic.List`1<UnityEngine.Renderer>) (at ./Packages/com.vrchat.base/Editor/VRCSDK/Dependencies/VRChat/ControlPanel/VRCSdkControlPanelBuilder.cs:1151)
VRC.SDK3.Editor.VRCSdkControlPanelWorldBuilder:VerifyMaxTextureSize (VRC.SDKBase.VRC_SceneDescriptor) (at ./Packages/com.vrchat.worlds/Editor/VRCSDK/SDK3/VRCSdkControlPanelWorldBuilder.cs:773)
VRC.SDK3.Editor.VRCSdkControlPanelWorldBuilder:OnGUISceneCheck (VRC.SDKBase.VRC_SceneDescriptor) (at ./Packages/com.vrchat.worlds/Editor/VRCSDK/SDK3/VRCSdkControlPanelWorldBuilder.cs:759)
VRC.SDK3.Editor.VRCSdkControlPanelWorldBuilder:CreateValidationsGUI (UnityEngine.UIElements.VisualElement) (at ./Packages/com.vrchat.worlds/Editor/VRCSDK/SDK3/VRCSdkControlPanelWorldBuilder.cs:251)
VRCSdkControlPanel:RunValidations () (at ./Packages/com.vrchat.base/Editor/VRCSDK/Dependencies/VRChat/ControlPanel/VRCSdkControlPanelBuilder.cs:883)
VRCSdkControlPanel/<>c__DisplayClass204_0:<ShowBuilders>b__1 () (at ./Packages/com.vrchat.base/Editor/VRCSDK/Dependencies/VRChat/ControlPanel/VRCSdkControlPanelBuilder.cs:822)
UnityEditor.RetainedMode:UpdateSchedulers ()