It happened to me once. Passenger side.
I had to replace the mechanism (in 2014).
https://www.aero-racing.co.uk/partsbooks/supersports/doorinternals.htm

With not too much hurry, I am waiting it happens on the driver side as well. Since it will... I know it. Probably in winter. While raining.

2010 Violet Aero Supersports | 2012 Green Vantage S Roadster