"lost atom" error with fix nve/npt command

Why does the ‘fix nve/npt’ command result in a ‘lost atom’ error when using periodic boundary conditions in the x, y, and z directions?

there is no such command in LAMMPS

I mean fix 1 all nve or fix 1 all npt

It is not the command that causes the error but either your geometry or your force field. Please see the (many) existing discussions in the forum archive.

Then please write what you mean. In the real of science it is always a benefit of being precise and detailed.