NoSuchFlowExecutionException Errors

[Hall, Gerry]

I am experiencing an issue where I get hundred/thousands of entries like the below like the below from an IP.  The IP varies and the error randomly stops with no interaction on my part - stopping/starting the IdP has no effect.  At this point, there does not seem to be anything malicious going on (had our security team investigate).

I initially blocked the IP(s), but this also prevented legitimate authentication requests originating from the IP.

The IdP is running Shibboleth v5.1.6.

Has anyone else experienced this issue, and if so, did you determine a solution?

xx.xxx.xx.xx|login.emory.edu|2026-02-12 21:36:32,412|9992BEDED070CBEE50D98AD64C274667| - ERROR [org.springframework.webflow.execution.repository.NoSuchFlowExecutionException:144] -
org.springframework.webflow.execution.repository.NoSuchFlowExecutionException: No flow execution could be found with key 'e1s1' -- perhaps this executing flow has ended or expired? This could happen if your users are relying on browser history (typically via the back button) that references ended flows.
at org.springframework.webflow.execution.repository.support.AbstractFlowExecutionRepository.getConversation(AbstractFlowExecutionRepository.java:172)
Caused by: org.springframework.webflow.conversation.NoSuchConversationException: No conversation could be found with id '1' -- perhaps this conversation has ended?
at org.springframework.webflow.conversation.impl.ConversationContainer.getConversation(ConversationContainer.java:124)
xx.xxx.xx.xx|login.emory.edu|2026-02-12 21:36:32,448|9AF5D704C4646B07C20525CE228E8D26| - ERROR [org.springframework.webflow.execution.repository.NoSuchFlowExecutionException:144] -
org.springframework.webflow.execution.repository.NoSuchFlowExecutionException: No flow execution could be found with key 'e1s2' -- perhaps this executing flow has ended or expired? This could happen if your users are relying on browser history (typically via the back button) that references ended flows.
at org.springframework.webflow.execution.repository.support.AbstractFlowExecutionRepository.getConversation(AbstractFlowExecutionRepository.java:172)
Caused by: org.springframework.webflow.conversation.NoSuchConversationException: No conversation could be found with id '1' -- perhaps this conversation has ended?
at org.springframework.webflow.conversation.impl.ConversationContainer.getConversation(ConversationContainer.java:124)
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