I don't know if the bug is that the ice doesn't melt in the end or that there comes no water when it's mined. However, it stays very irritating because there is no way of returning it to water in the end. It also doesn't drops itself when mined with silk touch. When multiple water sources next to eachother are frozen and mined, the water reappears. I don't know if it was the ice that I did mine that turned again into water or that it was only the  nearby water sources that updated their blockstates and turned again into water.