Thanks Nabeel.
This is what I am getting....
Backtrace: DB::write_debug > DB::query > PilotData::SaveFields > PilotAdmin->viewpilots > call_user_func_array > MainController::RunAllActions
Query: INSERT INTO phpvms_fieldvalues (fieldid, pilotid, value) VALUES (2, 1, '1234567')
Error: (1452) - Cannot add or update a child row: a foreign key constraint fails (`mysite/phpvms_fieldvalues`, CONSTRAINT `phpvms_fieldvalues_ibfk_2` FOREIGN KEY (`pilotid`) REFERENCES `phpvms_zzzz` (`pilotid`) ON DELETE CASCADE)
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The thing is phpvms_zzzz doesn't exist. I believe it was a table used early on to replicate the pilots table but since has been deleted.