Multiple errors are seen in the SMP logs related to NSE processing, here's an Event example:
Unknown inventory class (AutoClassRegistration=0), entire xml node skipped: '' (c7980d43-adb3-4fc4-a97c-a35a8a195aa5, '', ''), event id=541751064, from: ffc7426e-bfbc-48c1-a912-9b03f15c0d81, to: 'Basic Inventory Capture Item' (1592b913-72f3-4c36-91d2-d4eda21d2f96), @ 2022/08/23 12:57:07 PM (age: 00:00:23) at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
at System.Environment.get_StackTrace()
at Altiris.NS.ResourceManagement.DataClassImporter.InventoryLoader.EnsureDataClassItem(DataClassSignature dc)
ITMS 8.5, 8.6, 8.7
Component : Event Engine
The dataclass (guid c7980d43-adb3-4fc4-a97c-a35a8a195aa5 from above example) has been removed from the server.
Clients still have certain tasks which generate data for custom dataclass and once such NSE arrives SMP no longer knows how to process it and reports an event this dataclass information has been skipped.
Use the GUID seen in the logs to identify the event and then search the SMP database for the guid referenced to either find and restore the missing dataclass or locate items which may still reference them. Remove these if necessary to stop errors. The KB is available to help search the database.
171823 Find all tables that contain a specific GUID