It may be a used unit. We mark our EZL (ignition modules) with a paint marker to determine if they are ours or not. Sound like a warranty issue that you should take p w/ the shop.
1994 E500 (MY SUNDAY DRIVER)
1993 190E SPORTLINE LE W/ M104 SWAP
2000 BMW 528I (WIFEY'S CAR)
"Excuses are crutches for the unfounded."