The following error is observed in the AEM Dispatcher's log file:

Cause

This is a known product issue DISP-661.
Due to a change to allow Dispatcher logs to be multi-tenant the log levels were shifted by 1 in 4.2.3

Resolution

Increment the value of DispatcherLogLevel by 1 to fix issue.  i.e. use 1-5 rather than 0-4.

This may cause performance issues or affect your application.  As a solution, review the options below.