FEP.Maintenance.Workitem - disabled but causing XmlDefinitionReaderWorkItem error

Hello,

I have a bit of an issue with the FEP monitor on an Exchange 2013 Mailbox server. I have had some assistance from the SCOM team, and have followed the advise given but thisone server is still playing up.

After disabling the FEP check in the FEPActiveMonitoringContext, reboot, I get the following error appear in the event log every so often;

definitions were not created successfully:FEP.Maintenance.Workitem: An item with the same primary key 37 already exists in the table. Existing definition name: FEP.Maintenance.Workitem. New definition name: FEP.Maintenance.Workitem

Shortly after, this;

System.InvalidOperationException: Service MsMpSvc was not found on computer '.'. ---> System.ComponentModel.Win32Exception: The specified service does not exist as an installed service