In my (professional?) opinion, I would say the dealer is likely correct in stating it is unrelated. I would not suspect tinkering/replacement of the Rear SAM unit to cause an ABC system fault. In my 7+ yrs. MB dealer experience I have had several cars with ABC suspension throw an ABC malfunction out of the blue, where there was no problem previously. I would recommend having your dealer check the fault codes & explain to you exactly what the fault code is & what it pertains to. I would suspect it may be related to either: 1) a pressure supply problem, or 2) vehicle level problem. Whatever the ABC fault is for, I wouldn't suspect it's related to their Rear SAM repairs. Good Luck.