Review the deployimageactionhandler.log on the client in the windows\temp directory. This may point to a maptopreferrredserverhandler.log. That will give more insight into the failure.
Most likely you are getting an authentication error because of the mapped drives. When you set the image type to imagex or imagew v2 in 9.5 t will automatically map a driver for you, so you no longer need that action. If it tries to map again, and uses a different user, windows will reject the authentication.