In the log, I'm getting the following message:
[Toolbar] [WARN] button DevHelper.DHReloadGD has been created excessively often during the last 10 s - respective plugin may be behaving badly
This is because the plugin is calling ToolbarManager.Instance.add() during every OnGUI(). Instead, the button should be added exactly once (in Start(), for example), then held on to as long as necessary.