Get-CalendarDiagnosticLog - Returns partial information then errors out. Value cannot be null. Parameter name: Filename

I am attempting to gather calendar diagnostic logs for a room. 92 items are returned followed by an error.

Get-CalendarDiagnosticLog -Identity "chicago navy pier" -LogLocation C:\CalLogs

WARNING: An unexpected error has occurred and a Watson dump is being generated: Value cannot be null.
Parameter name: fileName
Value cannot be null.
Parameter name: fileName
    + CategoryInfo          : NotSpecified: (:) [Get-CalendarDiagnosticLog], ArgumentNullException
    + FullyQualifiedErrorId : System.ArgumentNullException,Microsoft.Exchange.Management.StoreTasks.GetCalendarDiagnostic 
   Log
    + PSComputerName        : Exchange02.site.com

Looking for some help in explaining this error.

Thanks

Environment:
 Exchange Server 2013 Cumulative Update 12 (CU12)15.0.1178.4