The Execute method of job definition Microsoft.SharePoint.Administration.SPUpgradeSiteCollectionJobDefinition threw an exception in Event Viewer

I am verifying the Event Viewer logs in my SharePoint server and found that there is an error with Event ID 6389.

Message: The Execute method of job definition Microsoft.SharePoint.Administration.SPUpgradeSiteCollectionJobDefinition (ID abd5b488-f6c1-4169-aa16-b26ee829b206) threw an exception. Collection was modified, enumeration operation may not execute.

What does this error means? What could be the reason and solution for this?

Thanks in advance