Indeed it is quite possible that the problem originates within Twig but you may or may not find it. If you re-create the object each time within the loop and the program now runs to completion, it would perhaps be worthwhile to at-least note it as a bug. It would also be interesting to see (if you find that re-creating the object each time does circumvent the problem) if repeatedly parsing the same file repeatedly using a single instance leads to the same core-dump behavior, because that would probably be repeatable by the package maintainer.