High Sierra System Print Pref Window Blank

No user modifications made to OS. Shut down one night. Next morning, document would not print.

Opened System Preferences > Printers and Scanners. "No printers are available." Blank window. Printers still in User/Library/Printers folder. System Library Printers folder restored (no apparent changes). Printers still not showing. Reboot. No luck.

Ran DiskWarrior from backup. Back to original partition. Printers appear. Shut down and restart. Printers disappear. Print Services issue notice. Rebuilt print services per Apple instructions. Reloaded printers from back-up.

Rebuilding directory temporarily helps, but shut down and boot results in printers disappearing every time.

Suggestions, Please.

Thanks!