Left turn signal won't cancel back to neutral position after turning wheel.

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Hello, The left turn signal does not cancel back to neutral after turning the wheel on my 1980 Firebird. I had a mechanic take the steeling wheel off and replace the turn signal switch. It worked a few times and now it stopped working. The lever does click twice trying to cancel but does not. I have to manually do it myself to shut it off. The right turn signal works fine and cancels back with no issues. The turn signal lever itself was "stiff" when depressed and he fixed that as well. I had people tell me that the cancel cam could be the issue but he insisted it was fine. Thanks for your help!