Water molecules fly out of box

Dear Users,
I am simulating a lipid bilayer in a box of water and I am using the following input file to equillibrate it. Unfortunately after some picoseconds that I visualize the system, I see that water molecules are scattering outward of the box.
Can anyone tell me why this happens?

You have dump_modify unwrap, which affects the treatment of PBCs for output. Please check the doc for it to see if it explains your result.

Thanks a lot Giacomo.