One of my clients did not close POS session for 1 year, due to some accounting issues, now it has more than 6000 pos orders and they want to close it. 
I have tried to close and it took more than 12 hours and yet could not reconcile all entries and throw a time-out exception. 

Is there a way to close the session manually, automatically, or using code or database queries? 
Any help will be highly appreciated. 
Thank you. 

*Note odoo version 10.