Undo group mismatch after checking render status

Hi there.

I have several comps in my Render Queue, and when I`m trying to run the code bellow,

after rendering first item AE freezes, render stops and alerts "After Effects warning: Undo group mismatch, will attempt to fix".

var rq = app.project.renderQueue;
app.beginUndoGroup("RenderItems");

try{
    // Start render    rq.render();    }catch(e){    alert(e.toString());
}

finally {
    app.endUndoGroup();
}

if (!rq.rendering){ alert("Finished");  }

My setup: AE CC2015 13.5.1. Win 7.

As far as I understood the problem goes on the last line while getting render status.

I`ve tried to add timer, but it didn`t help.

$.sleep (1000);
if (!rq.rendering){ alert("Finished");  }

The whole code works fine in all AE versions starting from CS6 till CC2015.

Does anyone have the same problem?

if (!rq.rendering){ alert("Finished");  }if (!rq.rendering){ alert("Finished");  }