How to rectify the error "Lost atoms: original 10802 current 10801"


I would like to deposit (Al , Ga ) atoms on an AlN surface but I find this error:Lost atoms: original 10802 current 10801.

In attachments the input file and the potentiel

Best Regards
in.sputter1 (1.8 KB)
GaNAl.sw (5.1 KB)
dd (340.6 KB)

When things don’t work, the first step is always to visualize your trajectory.
Are atoms supposed to leave the simulation?

Please read your input file carefully and compare each command with the corresponding documentation so you understand its purpose.