Extjs syncing a store gives me a url is undefined error under specific conditions

I have 4 grids that have the drag and drop plugin enabled. Their initial grid is dependent on a value from the db called state_id.

When I drop the selected row into a new grid, I update the state_id value and then tell it to sync up with the db and update the value for the item in question.

This works fine for the most part. I get this URL is undefined error when the following happens

1. User clicks drags row A from grid 1 to grid 2
2. User drags row A from grid 2 to grid 1
3. ERROR! Url undefined.

This error only seems to happen when the first item being added to the grid originally came from the same grid.

1. User clicks drags row A from grid 1 to grid 2
2. User clicks drags row B from grid 2 to grid 1
3. User clicks drags row A from grid 2 to grid 1
4. Works as intended!

drop event handler inside my controller:

dropit: function (node, data, dropRec, dropPosition) {
    if (node.dragData.records[0].store.$className == "AM.store.BacklogCards")
    {
        data.records[0].set('state_id', 1);
        this.getBacklogCardsStore().sync();
    }
    else if (node.dragData.records[0].store.$className == "AM.store.InprogressCards")
    {
        data.records[0].set('state_id', 2);
        this.getInprogressCardsStore().sync();
    }
    else if (node.dragData.records[0].store.$className == "AM.store.ReviewCards")
    {
        data.records[0].set('state_id', 3);
        this.getReviewCardsStore().sync();
    }
    else
    {
        data.records[0].set('state_id', 4);
        this.getDoneCardsStore().sync();
    }
    //node.dragData.records[0].store.sync();
},

Any ideas on what is causing this and how to fix it?

Thanks