Follow steps:-
1. Unjoin and rejoin existing master image and push it again. Prefer to rename master image name.
2. If this is not working, then you can make a anther
Persistent VM from this Master Image. Rename the VM name and unjoin, rejoin this VM to domain.
3. Try to push this new master image to existing desktop pool to get it updated. For me this solution has been worked.
4. If this is not work then make a fresh Master Image , update windows and try to push it. This is little time consuming but
I think this can also work as for me this solution worked.
i am facing same problem from many days and I used to troubleshoot in this ways as after each Windows update same problem coming . 