When was the last time you changed your water filter? Hollow cubes are the result of to little water in the mold and is usually caused by a restricted water filter, low water pressure, or restricted water flow to the ice maker. It is possible the water valve or ice maker went bad, but I would verify you have good water pressure to the refrigerator. Saddle type water valves are often a cause of restricted water flow.

Did you read my reply to your post? I offered some advice but you didn't comment on what I wrote. The ice on the back of the freezer, does it look like it is from the ice maker or is it in some other location? I am glad to assist you with your appliance questions, but there needs to be feedback.