Database write error while scanning files

We’re investigating an intermittent issue on a WordPress site where users occasionally receive the message “There has been a critical error on this website.” Refreshing the page typically resolves the issue.

To troubleshoot, I enabled WordPress debugging, updated Security by CleanTalk from v2.184 to v2.185, and ran a manual malware scan.

During the scan, the attached debug.log repeatedly recorded the following fatal error originating from the Security by CleanTalk plugin:

PHP Fatal error: Uncaught Error:
Class "CleantalkSP\SpbctWP\Scanner\Surface" not found

The stack trace references:

wp-content/plugins/security-malware-firewall/lib/CleantalkSP/SpbctWP/Scanner/ScannerQueue.php

In addition, the Malware Scanner reports:

“Database write error while scanning files.”

Could you please help determine:

1. Whether the fatal error and the database write error are related.
2. Whether either could be responsible for the intermittent WordPress critical errors we’re seeing.
3. Whether this is a known issue and, if so, whether there’s a fix or anything you’d recommend we do to resolve it.

I can provide screenshots and debug log.

The page I need help with: [log in to see the link]