1. can try use longer cron timing,maybe 18.10
2. tolerance 0.15
3. check the employees' timezone who not working

Two possible reason come to my mind:

• Automatic Check-Out from Settings -> Attendance -> Modes is a Company-dependent configuration. Ensure the checkbox is ticked for all Companies this configuration is relevant to
• The working schedule, as stated in the fields help text, is relevant: "Automatically Check-Out Employees based on their working schedule with an additional tolerance. Does not apply to employees with a flexible working schedule."
• • In addition: Are you sure all employees use the same working schedule (or at least a schedule that does not suggest planned resence post 6pm)?