*** ERROR # 4002 *** in OPTISTRUCT

I am doing with a nonlinear implicit problem in optistruct.

I have created contact surface and load steps (followed 'os-1500' for nonlinear implicit problem set up, apart from that created contact surface)

But while running its showing some errors

 

 *** ERROR # 4002 ***
 Running RADIOSS engine, 1 ERROR and 0 WARNINGs have been detected.
 They are listed below.

 ENGINE ERROR:
  ** ERROR : RADIOSS IMPLICIT STOPPED DUE TO MODELLING DATA **
       ISTOP=-1
 
  NLGEOM subcase        3, engine finished
 
(Running in-core solution)

 Volume                              = 6.87129E+006   Mass     = 1.05875E+001

************************************************************************

 ANALYSIS COMPLETED.

 

(1) How can I fix the issue?

(2) Is there any possibilities to edit the engine file in optistruct?