Agent Machines going to hung state

We have been using WPT private instance from last one year.Recently we started seeing some issue related to the Agent Machines. Sometimes while execute the tests the WPT driver going to hung state with the message “DNSFlushResolver Cache Returned 1”. After that it never any test those are pending in Queue.
Sometimes also we are seeing machine is going to restart.

-Initially we thought it might be resolved by updating to WPT version But after updating also we are seeing same issue.

Any suggestions for the above issue.Also we observed it is not writing the logs in the specified log folder in Urlblast.ini.
Is there any way we can write logs in Agent machine?

Attached is the screenshots for reference.