ECTS - Login error that persisted until IISRESET


This seem to occur randomly, here are the steps that I remember to the best of my abilities:
  1. Added 6 external users
  2. Approved all 6 users
  3. Login witih one of the newly created external users through extranet
  4. Got error message as below:
    value cannot be null.
    Parameter name: value at System.string.Endswith(String value, sfrinçComparison comparisonType)
    at Microsoft.sharePoint.ApplicabonRuntime.spRequestModule.PostAuthenticateRequestlHlandler(Object oSender, EventArgs ea)
    at System.web.HttpApplicabon.SyncEventExecubonStep.System.web.HttpApplication.IExecutionStep.Execute
    at System.web.lHlttpApplication.ExecuteStep(IExecutionstep step, Boolean& completedSynchronously)
    Troubleshoot issues with Windows SharePoint Services.
    And this error persists for any external users that tries to login thereafter until an IISRESET was done.