Flow restoration exception

[Wessel, Keith]

Hi, all, but probably just Scott,

Wondering if someone can tell me what the below indicates. We've got a professor who has been reporting intermittent login issues. Today, after incorrectly entering his password the first time according to the logs, he re-typed it and clicked log in again 21 seconds later. The result, rather than another attempt to validate his password against our password store, was this:

2019-05-22 15:38:10,203 - ERROR [org.springframework.webflow.execution.repository.FlowExecutionRestorationFailureException:76] [session=15j1zxrkhqnijlxpq502nr462] [ip=99.98.128.65] - 
org.springframework.webflow.execution.repository.FlowExecutionRestorationFailureException: A problem occurred restoring the flow execution with key 'e1s1'
	at org.springframework.webflow.execution.repository.impl.DefaultFlowExecutionRepository.getFlowExecution(DefaultFlowExecutionRepository.java:113)
Caused by: org.springframework.webflow.execution.repository.snapshot.SnapshotNotFoundException: No flow execution snapshot could be found with id '1'; perhaps the snapshot has been removed? 
	at org.springframework.webflow.execution.repository.impl.SimpleFlowExecutionSnapshotGroup.getSnapshot(SimpleFlowExecutionSnapshotGroup.java:73)
2019-05-22 15:38:10,204 - WARN [net.shibboleth.ext.spring.error.ExtendedMappingExceptionResolver:136] [session=15j1zxrkhqnijlxpq502nr462] [ip=99.98.128.65] - Resolved [org.springframework.webflow.execution.repository.FlowExecutionRestorationFailureException: A problem occurred restoring the flow execution with key 'e1s1'] to ModelAndView: reference to view with name 'error'; model is {exception=org.springframework.webflow.execution.repository.FlowExecutionRestorationFailureException: A problem occurred restoring the flow execution with key 'e1s1', request=Request(POST https://shibboleth.illinois.edu/idp/profile/SAML2/Redirect/SSO?execution=e1s1)@4c277009, encoder=class net.shibboleth.utilities.java.support.codec.HTMLEncoder, springContext=Root WebApplicationContext: startup date [Wed May 15 06:53:58 CDT 2019]; root of context hierarchy}

I'm used to seeing no such flow exceptions, but not flow restoration exceptions. What does it mean, and what can cause it?

Thanks,
Keith