I was over halfway into a copy and I accidentally clicked on the CLOSE (X) Button because there was another window overlapping the MakeMKV window and I clicked the wrong (X) Close Button. MakeMKV immediately closed and I had to start all over from scratch copying.
It would be nice if the program asked "Are you sure you want to close the program during a copy in progress?". It would sure make things less painful when you click the wrong button.