intermitent looping redirect with blackboard

[caleb racey]

We have an intermittent issue with our blackboard landscape and shibboleth.  The majority of users login successfully  but  we have users who get caught up in a looping redirect between the blackboard SP and the IDP. 
Out of 6000 logins to the idp coming from  blackboard today the logs show roughly 600 getting caught up in a looping redirects. Our blackboard landscape is 5 front end servers behind a load balancer (A10), sessions on the blackboard SPs  are being written  to and read from a shared  database so they should all have access to the same shib session information, we have one live IDP.

Has anyone experienced this kind of problem before and have tips of what to look for to avoid the issue?

Regards

Cal