Here's my setup: I have two Tomcats using PersistentManager with FileStore to store sessions on a NFS they both have access to. Inside the session there's an object which contains a map. I also have a request listener that logs the contents of the map on every request.
I kill one Tomcat and I can see in the session file that the map contains two keys. I then make a request to the remaining Tomcat and I can see the map contains only one key. The only way I can think of that that would happen is if the map was only partially loaded from the file. Is that even possible? Any good ideas on how to debug this?