Yes etickets were in use.
The problems stemmed from sending copies on phones to friends.
So when the barcode was presented to the turnstile, only the first barcode of the ticket was accepted ( if my understanding of this is correct).
So in effect a fake could go through if presented before the original, leaving the person who bought the original ticket stuck at the turnstyle, and refusing to move causing a bottleneck of their own doing but trying to make out it was everyone elses fault.
Then you had the people with the fakes also refusing to move before realising that their only chance of entry was to commit a criminal act and open a safety gate.