Based on the logs looks like ConcurrentModificationException is originating from the ConfigurationClassParser. Try below steps to drill down the actual issue

1. Ensure that no concurrent modifications are happening in any of your configuration classes.
2. Given you are using spring-boot-1.3.3.RELEASE, consider upgrading to a more recent version if possible.
3. Review your configuration classes to ensure that any @Import or @Configuration annotations are not causing concurrent modifications.
4. If you have any custom configuration, ensure that no collections are being modified while they are being iterated over.
5. If already done above steps, Try to Debug the issue by adding Exception Breakpoint for ConcurrentModificationException