Issue with the external tiers where suppliers login to participate in sourcing events?

We have had issues with the external tiers where suppliers login to participate in sourcing events. Almost every other week when the suppliers login and click on Sourcing Homepage they get an unexpected error. When they click on 'here' link, they get the JBO-25036 error. Sometimes the issue is fixed when the supplier clears the system cache/cookies but on few other instances we have to bounce the external tier as most suppliers face the same issue. Suppliers encounter the same error when they try to check their PO's or invoices on the external tier. Have you encountered such issues on