When using the EventBus by code it is the responsibility of the user to Register and Unregister the events. Because in the user's code the event has not been unregistered, it is normal that it creates errors between PlayModes as the EventBus is static so it keeps every reference that have been registered. Here is how the code should look like to avoid errors:

public class DemoScript : MonoBehaviour
{
Delegate m_DoWork;

void Start()
{
Action<int> dw = i => DoWork(i);
m_DoWork = dw;
EventBus.Register<int>("DoWork", dw);
}

private void DoWork(int obj)
{
Debug.Log(this.name + "DoWork");
}

void OnDestroy()
{
EventBus.Unregister("DoWork", m_DoWork);
Debug.Log("OnDestroy");
}
}