Got symbol already defined error when updating project from UE 5.2 to UE 5.5

Development Programming & Scripting C++
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My static Class Member in my plugin got LNK2005 Error : symbol already defined in object when I was trying to update my project to UE 5.5, and it can work correctly in UE 5.2

source codes are below:

These code comes from the plugin:

SoulConnect.h

// All Right Reserved

#pragma once

#include "CoreMinimal.h"
#include "Engine/DataAsset.h"
#include "SoulPerkTree.h"
#include "SoulConnect.generated.h"

USTRUCT(BlueprintType)
struct FSoulConnection {
    GENERATED_BODY()
public:
    ...
    static double ConnectionWeight;
};

double FSoulConnection::ConnectionWeight = 0.005f;

SoulConnect.cpp

// All Right Reserved

#include "SoulConnect.h"

FPrimaryAssetId USoulConnect::GetPrimaryAssetId() const
{
    static const FPrimaryAssetType AssetType = TEXT("SoulConnect");
    return FPrimaryAssetId(AssetType, GetFName());
}

And PerkTreeActorComponent.h used that header in include, and it(PerkTreeActorComponen) is in my project UE511SV2K

Current Problem is:

FSoulConnection::ConnectionWeight has already defined

in Module.UE511SV2K.cpp.obj
(Raised by PerkTreeActorComponent.cpp.obj / USoulTreeRenderUMG.cpp.obj)

and in Module.SoulTreeDisplayer.cpp.obj
(Raised by SoulConnect.cpp.obj / SoulTreeDisplayer.cpp.obj / SoulTreeEditor.cpp.obj / SoulTreeRenderWidget.cpp.obj)

I’ve tried some ways to solve this issue:

  • Delete the implement of ConnectionWeight:
    Got error LNK2001 unresolved external symbol （from SoulTreeRenderWidget.cpp.obj / PerkTreeActorComponent.cpp.obj)
  • Move the implement of ConnectionWeight into cpp file (cut and paste)
    Got error LNK2001 unresolved external symbol (from PerkTreeActorComponent.cpp.obj)
  • Use double FSoulConnection::ConnectionWeight; in .h and FSoulConnection::ConnectionWeight = 0.005f; in .cpp
    Got C4430 missing type specifier in SoulConnect.cpp where FSoulConnection::ConnectionWeight = 0.005f; located
    and C2371 redefinition in SoulConnect.h where double FSoulConnection::ConnectionWeight; located.

Why should this happen? Can anybody help?