A well-known issue. Over the course of time the iPhone Cable isolation becomes damaged and you need to buy a new one. But with this repair kit you will be able to use your Cable until you buy a new iPhone.
3D printing settings
Print 1x iPhoneCableCoverB and 1x iPhoneCableCoverT.
Use sandpaper or a small file to clean the iPhoneCableCoverT so you can push it into the iPhoneCableCoverB.