Issue with sonar java:S1948

I have a problem with understanding why I have an issue with SonarLint Intellij plugin:

public enum AuftragMessageStatus {
    SUCCESS, ERROR
}

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class AuftragMessage implements Serializable {
    private static final long serialVersionUID = 2405172041950251808L;
    private AuftragMessageStatus status;
    private String text;
}

import lombok.Getter;
import org.springframework.context.ApplicationEvent;

@Getter
public class AdminAuftragEvent extends ApplicationEvent {

    private final AuftragMessage message;

    public AdminAuftragEvent(final Object source, final AuftragMessage message) {
        super(source);
        this.message = message;
    }
}

I get critical java:S1948 issue: Make "message" transient or serializable. What is wrong in my code? Or that is simple plugin bug?

Thanks in Advance, Wladi