Who can tell? Could be harmless, could be a bug, could be a mistake on your side.
But since you are not telling us what king of simulation of what kind of system with what version(s) of LAMMPS on how many processors with what kind of command line on what kind of architecture and OS you are running, and also not telling us how you know which is the "correct" result and how different the different result is, the *real* mystery here is how you can expect a meaningful, well-founded response.
Please ask smarter questions, and you'll get smarter (and less aggressive) answers.
P. S. : there is an entire web page dedicated to show people how to ask smarter questions (about software), BTW.
Dr. Axel Kohlmeyer akohlmey@...24... http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.