TileGrid - fetchData does not update

SmartGWT 5.0p / Firefox 26

The 1st time I call TileGrid.fetchData(criteria), the Tile image is updated correctly.

However, on all subsequent calls to TileGrid.fetchData(criteria), the Tile image is never updated.

I've verified via the RPC tab and DSCallback that the data is in fact fetched correctly. However the Tile is never updated.

Any suggestions on this issue?