Not All Downloaded Work Units Are Being Processed Simultaneously

I'm running Einstein at Home on a Raspberry Pi model 2B which has four processors. Typically, four work units are downloaded and processed simultaneously. However, I've noticed that for the past day or so, only three of the four work units are being processed at one time. Information for the fourth unit says:

scheduler state: uninitialized
active_task_state: UNINITIALIZED

Why the change from the previous methodology?

I assume there's nothing I need to do to start processing that fourth work unit, but if that's not the case, please advise me on the steps I need to take so the full resources of the computer can be used for all of the downloaded work units. Thank you.