LazyInitializationException from object stored in the HTTP session - spring

Question

I have a scenario in a Grails project where I am storing domain object in an HTTP session. This is arguably not a great practice, but I'm not in a position to change that at the moment.
The issue I'm encountering is that if I hit an unhandled exception, and then attempt to logout (authentication is using Spring Security) I will be unable to logout and will get another LazyInitialization exception (not even on the same collection as before.)
What I don't understand is what Spring Security is trying to do with these detached domain objects in the HTTP session.
If I look through the Grails docs, there are examples on how to reattach things to the Hibernate session: http://grails.org/doc/latest/ref/Domain%20Classes/attach.html. In this case though, I don't even want to reattach these objects. I'm done with them. It seems like spring security is looking in the HTTP session and trying to do something with those objects, but I'm not sure what, or how to fix it.
Full stack trace:
Line | Method
->> 1418 | writeOrdinaryObject in java.io.ObjectOutputStream
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 1177 | writeObject0 in ''
| 1547 | defaultWriteFields in ''
| 1508 | writeSerialData in ''
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 1547 | defaultWriteFields in ''
| 1508 | writeSerialData in ''
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 347 | writeObject . . . . in ''
| 1128 | writeObject in java.util.HashMap
| 988 | invokeWriteObject . in java.io.ObjectStreamClass
| 1495 | writeSerialData in java.io.ObjectOutputStream
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 1547 | defaultWriteFields in ''
| 1508 | writeSerialData in ''
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 1547 | defaultWriteFields in ''
| 1508 | writeSerialData in ''
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 1547 | defaultWriteFields in ''
| 1508 | writeSerialData in ''
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 347 | writeObject . . . . in ''
| 1129 | writeObject in java.util.HashMap
| 988 | invokeWriteObject . in java.io.ObjectStreamClass
| 1495 | writeSerialData in java.io.ObjectOutputStream
| 1431 | writeOrdinaryObject in ''
| 1177 | writeObject0 in ''
| 347 | writeObject . . . . in ''
| 74 | doFilter in grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter
| 1145 | runWorker . . . . . in java.util.concurrent.ThreadPoolExecutor
| 615 | run in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run . . . . . . . . in java.lang.Thread