non-positive volume in in-cylinder 3D
 

i am doing cylinder-piston arrangement in 3D. for that i m using dymnamic mesh and in-cylinder as dynamic mesh parameters. but if i give mesh motion then for first 12-15 time steps, it is showing motion and after that it is showing non-positive volume and no further mesh motion. i tried more fine mesh, even then same problem. please help me to sort it out.