Why is docker build suddenly not working?

I am using docker build to create my docker images and then I push them to my own registry. This used to work perfectly. Now all of a sudden for no reason what so ever, docker has started to fail when I want to build my docker image. I get this message:

COPY failed: stat /var/lib/docker/tmp/docker-builder658739121/target/Project.jar

As you can see docker is trying to copy the jar from a temporary directory and not from the location I have supplied!!! This used to work and all of a sudden docker has started to F**K UP big time. I CAN NOT BUILD BECAUSE OF THIS BLUNDER!!!

When I google this error there a lot of people complaining. Why has docker not fixed this???

Docker used to be good, now it’s completely worthless and pathetic.