There were two problems:
1) Only 2 attributes were recognized due to getter naming
2) The @PostConstruct method was private. It's supported by the annotation but not by JCasC.
Due to 1), we were not able to configure everything in JCasC, and due to 2), if you try to configure it, it will break your instance due to the MessageDigest not being initialized => all requests will have an invalid crumb token.