Is this standard fit or fault they tend to develop. Last car I had with this deliberate feature was a Citroen. TBH, I prefer them not to cancel themselves.
From new they self-cancel. For about 6 months. After that they need a helping hand. I replaced the indicator stalk with a new one - but it soon went back to its old ways. I'm used to it now.
If you change your mind there is [url=https://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=633715#Post633715]this how-to[/url
My own fix is based upon reducing the play around the central white nylon cylinder by inserting one or two O rings around it; a second approach is to increase the efficiency of the spring which returns the jaws/teeth to position.