using plane for comression

Hi All,
I am trying to make a compression test on a structure. I have defined 2 planes: one the upper plane and the other is the lower plane. for some reason, when the upper plane moves down to do the compression, it stops after 3 steps, and the simulation doesn’t run any more without any error.
Here is the part of the out put:

LAMMPS (16 Feb 2016)
Reading restart file …
restart file = 16 Feb 2016, LAMMPS = 16 Feb 2016
orthogonal box = (-50 -50 -50) to (50 50 50)
2 by 2 by 5 MPI processor grid
17044 atoms
Finding 1-2 1-3 1-4 neighbors …
Special bond factors lj: 0 0 0
Special bond factors coul: 0 0 0
0 = max # of 1-2 neighbors
0 = max # of 1-3 neighbors
0 = max # of 1-4 neighbors
1 = max # of special neighbors
Resetting global state of Fix 1 Style nvt from restart file info
Neighbor list info …
2 neighbor list requests
update every 1 steps, delay 0 steps, check yes
max neighbors/atom: 2000, page size: 100000
master list distance cutoff = 12
ghost atom cutoff = 12
binsize = 6, bins = 17 17 17
Setting up Verlet run …
Unit style : real
Current step: 0
Time step : 0.2
Memory usage per processor = 61.9257 Mbytes
Step PotEng TotEng Temp uwall[3] dz
0 -2519963.2 -2504763.1 299.20358 0 0
50 -2519891 -2504784.8 297.35569 0 -0.0008
100 -2519861.9 -2504550.1 301.40077 0 -0.0016

I appreciate any help on this.

Try running on a single processor and print thermo output
every step. If you are compressing a system and do
it (for example) too quickly, then things can blow up. The
thermo output may tell you this.

Steve