Some 2004-15 Mazda models (complete list below) may produce a clunk, bang or jolt from the front end on initial movement following a long period of inactivity (usually overnight).
According to Mazda, the problem usually develops at about 6 mph or less, and is nothing more than ABS/TCS/DSC systems performing a normal initialization sequence prior to vehicle take-off.
Make your customer aware of the situation and note it for future reference.
Vehicles that are most susceptible to the histrionics are 2004-11 RX-8s; 2006-14 Miatas and Mazda5s; 2007-12 CX-7s; 2007-14 MAZDA3s and CX-9s; 2011-14 Mazda2s; and 2013-15 CX-5s.