Still sounds extremely unlikely. If a model of car has a particular design flaw, you'll expect to hear a lot of reports of that model suffering the same malfunction, but you wouldn't expect to hear that dozens of units within a certain radius suffered the same malfunction simultaneously. You'd need to subject them all to some sort of outside interference at the same time for that sort of occurrence to be plausible, and an event of that scale ought to leave evidence beyond its effect on all the pacemakers in the vicinity.