Hotel Tango, you'd be right enough if it was a minor defect, but something that causes an engine failure or shutdown should not be recurring so soon, especially on an ETOPS flight.
With ultra-reliable systems (generally and not just aircraft), following a failure the most likely subsequent problem will be "same system" and "very soon". Usually for the reasons described by tdracer.
This does not necessarily reflect on the diligence of the maintenance crew. If a problem cannot be reproduced consistently under test, and if no definitively defective components can be identified then how is one sure that the repair is complete?