data-at-rest enabled high CPU use for long times

Either when creating a new database to have data-at-rest enabled, or adding new tables to database with other data-at-rest tables, or database startup with data-at-rest employed - there are times when all of the data-at-rest background tasks are consuming 80-90% of multiple relatively fast CPU's anywhere from 20 minutes to 6 hours on systems with 32GB RAM.

There doesn't appear to be any consistent and determinable cause for the overly long utlizations.