Workflow background process never completes

We have 2 non-prod EBS environments where the Workflow Background Process conc request is running but never seems to complete.  It does seem to be processing...but very slowly.  We are running with the parameters Deferred=Yes, Timeout=Yes, Stuck=No.  We've seen this in the past but have never been able to identify the crux of the problem.  Both environments have recently been cloned from production (and we're not seeing this in our prod environment) and after cloning it runs fine but then eventually something is taking place to cause the process to run for endlessly.