Hi @Eric Welshons ,
The error means it is looking for something that's not there. The errors are ultimately benign (and thus ignorable although annoying).
Here is the similar post, please refer to it:
https://social.technet.microsoft.com/Forums/en-US/521c45d1-803a-4aea-88bd-7296cc0b19bf/mysterious-3rd-party-update-errors-in-windowsupdatelog-file?forum=ConfigMgrCompliance
How do we stop this from filling the log on the clients?
Do we mean we just unsubscribe Dell and Lenovo 3rd party catalogs? We could configure the tab of Enable third party software update as NO in client settings, and cancel the tab of Enable third party software update in SUP component properties.
Here is the screenshot we could refer to:
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