try these links
DS4 front door panel dissasembly - General Discussion / Technical Documentation - DS Forums
Sticky Door Handle - General Discussion - DS Forums
DS know the sticking of handles is an issue many owners are experiencing, yet they refuse to open an official call back.
Water ingress into the “sealed” plastic mechanism seems to be the main issue so it’s possibly more of an in in the UK due to wetter climate.
My dealership hold the handles as a stock item due to the numbers having to be replaced.