Can't put random servers in Maintenance Mode - SCOM 2022

Hi everyone,

Recently I've been getting an error trying to manually put random servers in to Maintenance Mode. We have an estate of 250+ servers being monitored. Monitoring is fine, they behave as expected yet when I try and put a hand full in to Maintenance Mode we get the following error:

The client has been disconnected from the server.  Please call ManagementGroup.Reconnect() to reestablish the collection.

Date: 01/10/2025 09:52:44

Application: Operations Manager

Application Version: 10.22.10928.0

Severity: Warning

Message:

Microsoft.EnterpriseManagement.Common.ServerDisconnectedException: The client has been disconnected from the server. Please call ManagementGroup.Reconnect() to reestablish the connection. ---> System.InvalidOperationException: The monitoring object is already in maintenance mode.

   --- End of inner exception stack trace ---

   at Microsoft.EnterpriseManagement.Common.Internal.ExceptionHandlers.HandleChannelExceptions(Exception ex)

   at Microsoft.EnterpriseManagement.Common.Internal.ServiceProxy.HandleFault(String methodName, Message message)

   at Microsoft.EnterpriseManagement.Common.Internal.AdministrationServiceProxy.StartMaintenanceMode(Guid managedEntityId, DateTime startTime, DateTime scheduleEndTime, Int32 reason, String comments, Boolean recursive)

   at Microsoft.EnterpriseManagement.Monitoring.PartialMonitoringObject.ScheduleMaintenanceMode(DateTime startTime, DateTime scheduledEndTime, MaintenanceModeReason reason, String comments, TraversalDepth traversalDepth)

   at Microsoft.EnterpriseManagement.Mom.UI.MaintenanceModeDialog.<OkButtonClick>b__12_0(Object <p0>, ConsoleJobEventArgs <p1>)

   at Microsoft.EnterpriseManagement.Mom.Internal.UI.Console.ConsoleJobExceptionHandler.ExecuteJob(IComponent component, EventHandler`1 job, Object sender, ConsoleJobEventArgs args)

System.InvalidOperationException: The monitoring object is already in maintenance mode.

The servers are not in Maintenance Mode, I have confirmed this with PowerShell. I have rebooted OMS and DB servers. I can't find anything online to re-establish the connection. Any help appreciated. I have a DV environment which can Maint Mode the servers in question fine, so it is SCOM rather than the server client.

Thanks in advance,

Sean