Noticed this behavior today:
CronParser parser = new CronParser(CronDefinitionBuilder.instanceDefinitionFor(CronType.UNIX));
ExecutionTime time = ExecutionTime.forCron(parser.parse("0 * * * 1-5"));
time.nextExecution(new DateTime(2016, 2, 29, 11, 0));
Expected output: 2016-02-29T12:00:00.000-06:00
Actual output: 2016-03-02T00:00:00.000-06:00
Omitting the day-of-week specifier in the crontab returns the correct result.