For those how are interested: It is not a concurrency problem! But a problem of SoftReferences being caught by GC.
I have just added a patch to the jira issue and if someone come a cross a stacktrace like
in the logs sometimes and swears 'MyBean' has a getter for 'id' than your're "lucky" to have the same strange behaviour and should vote for SPR-9059
org.springframework.beans.NotReadablePropertyException: Invalid property 'id' of bean class [org.test.MyBean]: Bean property 'id' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?