Mridanga has a gap between the head and body

There is a gap between the head and the rubber bumper on the Tilak Mridangas by design. 

If we don't leave this gap, then as you tune the heads the heads stretch and close this gap which will eventually make it impossible to remove or fit the rubber bumper.

So the gap will reduce over time, but it has to be there to allow proper tuning.

This is not a fault, it is by design, and it is to enable tuning of the drum properly.