dynamic mesh not working
 

gays please help.
i have a problem in dynamic meshing . i want to move a body (70kg) by giving it initial pressure of air (6 bar) from bottom pressure inlet in two phase (first in water and then in air).
2d geometry. with triangular mesh .
i used vof model,implicit body force on , k-epsla with realizable and scale-able wall function. having secondary phase water. turned on the specific density of air in operating conditions.
turned on smoothing (spring constant=0.2) and re-meshing (maximum and minimum cell size according to info, cell skewness=0.2) . create the 6dof file in setting defining one DOF translation x=0 and y=1 with zero constant and pre-load, defining certain mass.
in dynamic meshing ( created the body with giving its center of gravity value and define it as rigid body ).initialize the solution from pressure inlet. and patch the regions of water and air ,simulation runs correctly.
but when i turned off the one DOF and define the moment of inertial values my calculation does not proceed it stopped after ist time step in the beginning (negative cell volume detected) i make sure to decrease low time step but does not work.
suggest me what to do ..is there meshing problem or setting.. i will be very thankful .