People report fixing this by spraying contact cleaner into the turn signal switch. Otherwise try replacing it.
Problem is intermittent but essentially the turn signals continue to blink after the control stalk returns to the neutral position. Swapped the relay and still have the problem so I'm guessing it's the control stalk that's failing. Am I forgetting anything else that could cause this problem? I'm going to pull the stalk, burnish and clean the contacts, and try it again but if someone has experienced this problem and found the cure I wouldn't mind hearing about it.