Another thing I can suggest you is to temporarily disable ViewState compression just to ensure it is not interfering with the AppFabric SessionState caching and see if you still get exceptions.
Also if you have set runAllManagedModulesForAllRequests
property to true
, could you please try removing it and add preCondition="managedHandler"
and let me know if the issue still persist.
Also is the exception is thrown on all pages which has RadButton on only on some pages? If this is the case I would suggest that you review the following forum thread:
Stop compression for a separate page
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