The preload queue gets stuck at 99% completion when the final step of processing fails. The system encounters files that cannot be fully processed. Resource exhaustion prevents completion. Cache or queue corruption occurs. Plugin conflicts interfere with the final stages. Database issues slow down the tracking mechanism. Network or storage instability causes repeated failures. A bug in the preload logic might prevent proper completion.
This issue prevents associated features like full site caching from functioning correctly. The process consumes resources without completing, potentially causing performance degradation. The error typically shows no specific error message, just a frozen progress indicator at 99%.