Is IIS on your CM12 Site Systems properly configured ? An easy way to monitor (and automatically fix) your settings is using the compliance settings management from Configuration Manager 2012…
Based on Prerequisites for Site System Roles , I’ve created a DCM Baseline example that monitors and fixes IIS configurations and missing Server features that are used on ConfigMgr2012 Site System Roles …
Note: This is just an example… do not enable auto remediation if you are not 100% sure what the CI’s are doing… ! Use at your own risk.
Download the DCM Baseline here:
IIS Configuration for CM12.cab