.ERR are log files sent by clients to report their status and that SEPM was not able to process. Therefore, correct information about real client status (definition up-to-date, etc.) might be inside these files and explain why you have out-of-date information in the console.
You can open ERR files with notepad and try to identify which machine it is coming from. There might be some errors in SEPM logs as well that describe what's wrong with such files (you would need to open a ticket with the Support for such troubleshooting).
This can usually appear if you have an older version of SEP client managed by a newer SEPM release.
Try to update the client and see if it helps.