I've read of this happening before, but a search didn't turn up the thread I was looking for.

My mother used her Aeroplan miles to issue an award on UA. Last week upon check-in at YVR, she was bounced between AC & UA while they tried to issue the ticket in time for her flight. She said UA issued her BP before AC resolved it so she could make it through US Customs and Immigration. She made her flight, but it could have easily been a bigger problem

How can they justify instances of failing to issue tickets? It seems to be an ongoing issue. I'd expect that they'd have internal minimum standards to uphold.