What we know is a ticket is unable to close so we can not do NEW day anymore . We instruct customer to reboot the system, after that it is still there.
We login at the night , I open the problem ticket, I was able to add a line, order a item, I change the price to one cent, then I can go ahead to cash out, then it is gone.
It is a simple way to clear a jammed ticket .
It may works for you.