Ive had 2 that have had the same issue:
Year: 2011 2.5i premium sedan
Miles: 3k
Signal: Driver side
resolution: Dealer replaced turn signal, said it was a known issue.
Year: 2012 STi Hatch
Miles:6k
Signal: Drivers side
resolution: reaching back and wiggling the wires resolved the issue. Currently at 14k miles and have not seen the issue since.