ABAQUS ALE gives random solution

Hi all,

I am simulating an excavation problem using the ALE method. If I rerun exactly the same input file only changing the duration of the last (long) step and compare results of the two analyses at the same analysis time I get significantly different results (e.g. up to 20% different settlements). I have tried changing the last step duration and I get different results again. How can this be? I am really worried about this behaviour!

Regards