The reservation screen

The visiting groups had booked seats through two systems that did not update each other. A school amended its numbers by email after the online list had been printed. Another booking appeared twice under slightly different names. Several seats had to remain available for wheelchair users and companions, but those spaces were not marked on the paper chart. The group leaders were already waiting outside when the screen froze. We began checking each booking against its confirmation rather than treating either the screen or the printout as a complete record.

Describe the difficulties of producing an accurate seating plan. You may support your points with brief quotations.