Creating a water area in a mountain biome above snow level won't result in ice forming as usual. Only one or none ice blocks will form, unless closing the world and reload it again. Ice formation behaves as expected after reloading.
Since ice formation is dependent on light levels this might be related to the latest lighting glitches and its fixing.
Can confirm that I am experiencing this issue. I left an attachment; it shows an ice farm I made in a mountain biome on a server I play in.