Modeling 2012 R2 domain controller causes 100% CPU

Just did a fresh install of Core 5.1.3 after having piloted Zenoss back in the 5.0 period. If I add any of our 2012 R2 domain controllers and try to model themit fails in Zenoss (reports that it lost connection with WinRM). On the DC, the svchost.exe responsible for WinRM jumps to 100% CPU indefinitely until the DC is rebooted. This does not happen with our 2008 R2 DCs, and does not happen on 2012 R2 machines that are not DCs. I would greatly appreciate any thoughts or pointers. Versions:

Zenoss Core 5.1.3

Zope 2.13.13

Python 2.7.5

ZenPacks.zenoss.PythonCollector 1.7.4

ZenPacks.zenoss.Microsoft.Windows 2.5.13 (upgraded from the 2.5.12 that was included with 5.1.3 install).

Excerpt from discovery job log:

2016-06-29 20:18:20,105 INFO zen.ZenDisc: Discovered device drdc01. 

2016-06-29 20:18:20,105 INFO zen.ZenDisc: Result: drdc01 

2016-06-29 20:18:20,172 INFO zen.ZenDisc: skipping WMI-based collection, PySamba zenpack not installed 

2016-06-29 20:18:20,176 INFO zen.ZenDisc: Python collection device drdc01 

2016-06-29 20:18:20,176 INFO zen.ZenDisc: plugins: zenoss.winrm.OperatingSystem, zenoss.winrm.CPUs, zenoss.winrm.FileSystems, zenoss.winrm.Interfaces, zenoss.winrm.Services, zenoss.winrm.Processes, zenoss.winrm.Software 

2016-06-29 20:18:20,394 INFO zen.ZenDisc: No command plugins found for drdc01 

2016-06-29 20:18:20,394 INFO zen.ZenDisc: SNMP monitoring off for drdc01 

2016-06-29 20:18:20,395 INFO zen.ZenDisc: No portscan plugins found for drdc01 

2016-06-29 20:20:23,110 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,439 WARNING zen.ZenDisc: Client drdc01 timeout 

2016-06-29 20:21:20,439 INFO zen.ZenDisc: Scan time: 180.33 seconds 

2016-06-29 20:21:20,440 INFO zen.ZenDisc: Daemon ZenDisc shutting down 

2016-06-29 20:21:20,444 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,445 INFO zen.publisher: publishing failed: [>] 

2016-06-29 20:21:20,445 INFO zen.publisher: queue still contains 3 metrics 

2016-06-29 20:21:20,445 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,448 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,448 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,450 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly. 

2016-06-29 20:21:20,451 ERROR zen.PythonClient: Connection lost for drdc01. Check if WinRM service listening on port 5985 is working correctly.