Typos frequently cause errors when epix is run; the compiler generally issues a helpful message, naming the troublesome line of the input file and the type of error.
Two common sources of error in a syntactically correct input file are camera mis-placement and non-generic intersections. If the camera is too close to objects in the scene, the lens may try to divide by zero (or by a small epsilon), resulting in nan errors (or very large coordinates) in the output file. In this situation, epix will succeed, but elaps will hang. By contrast, an error message of the form
/usr/local/bin/epix: line 275: 27333 Aborted ...signifies an uncaught exception, hence a non-generic intersection.
Though the shell scripts are extensively tested, they are a possible source of runtime problems. (For example, elaps tries to pass options to the compiler while reserving other options for its own use, all while trying to deal intelligently with malformed commands.) If a script does something unexpected, it's probably a Feature, not a Bug. In any case, please notify the author of anomalous behavior.