[SmartCrawl] URL Crawler error

The URL Crawler feature is consistently returning the following error on several of my sites:

“Your SEO crawl has timed out due to an unknown error. Please try again or contact support.”

This is happening on both multisite sites with or without mapped domains (through your Domain Mapping plugin), and sites in multisites with no domain mapping at all, and it’s happening on some single site installs as well.