How to set struct value using UScriptStruct::ImportText()

i am trying to set a “linera colour” variable"s value using ReflectionSystem"s ImportText() .
declaration of that func is:
//Source\Runtime\CoreUObject\Public\UObject\Class.h
/**

 * Sets value of script struct based on imported string
 *
 * @param	Buffer			String to read text data out of
 * @param	Value			Struct that will be modified
 * @param	OwnerObject		UObject that contains this struct
 * @param	PortFlags		EPropertyPortFlags controlling import behavior
 * @param	ErrorText		What to print import errors to
 * @param	StructName		Name of struct, used in error display
 * @param	bAllowNativeOverride If true, will try to run native version of export text on the struct
 * @return Buffer after parsing has succeeded, or NULL on failure
 */
COREUOBJECT_API const TCHAR* ImportText(const TCHAR* Buffer, void* Value, UObject* OwnerObject, int32 PortFlags, FOutputDevice* ErrorText, const FString& StructName, bool bAllowNativeOverride = true);

and here is my code:

UFUNCTION(BlueprintCallable, Category = "ReflectionSystem|Variables")
    		static int SetMembersOfStructVariable(UObject * Target, FString varname, FString valueString, TArray<FStructMembers>& structProperties, FString& fullDesc)
    	{
    		if (varname.Equals("AttachmentReplication"))
    			return -22;
    			
    		const UStruct* Owner = Target->GetClass();
    
    		UProperty* prop = Owner->PropertyLink;
    		const FName PropertyName(*varname);
    		prop = FindField<UProperty>(Owner, PropertyName);
    
    		UStructProperty* objectProp = FindField<UStructProperty>(Owner, PropertyName);
    		if(	(objectProp != nullptr) && (prop != nullptr) )
    		{
    			FReflectionSystemBFLOutputDevice2 SaveErrors;
    			if (prop->GetClass() == UStructProperty::StaticClass())
    			{
    				int32 PortFlags = 0;
    				objectProp->Struct->ImportText(*valueString, prop, Target, PortFlags, &SaveErrors, objectProp->GetName(), true);
    			
    			}
    		}
    		return 1;	
        }

using breakpoints, i have tested that ImportText() does it work fine. without any exception or error.
but 2/3 second later ue4 just crashes.

in between that 2/3 second if i try to print that variable then again it crashes inside:

void UObject::execInstanceVariable(FFrame& Stack, RESULT_DECL)
{

}

the error is:

Exception thrown at 0x00007FFA4CABC917
(UE4Editor-CoreUObject.dll) in
UE4Editor.exe: 0xC0000005: Access
violation reading location
0xFFFFFFFFFFFFFFFF.