Problem when extending windows partition using Disk Utility
Use Hard Disk Manager to repair and partition BOOTCAMP. 

You can get Hard Disk Manager from here (https://www.paragon-software.com/hdm-mac/#) or here (includes trial reset) (https://nofile.io/f/aWdNwtb3Ry9/Hard.Disk.Manager.v1.3.873.dmg) (link will expire in 24 hrs)