Are you clearing the snow aroud the hive? This could add to frost heaves. I know in my yard everything stays level except paths where I clear the snow. Those areas get more exposed to the cold and heave up like crazy. Just a thought.
Ern

One piece of of platform could work better for you.
Good foundation is important, what really works well for me is some
left over pieces of roofing material, it is Styrofoam, about 8 inches thick
with wood attached on one or two sides, some pieces are as big to fit
one hive on top, some pieces I have for 2 hives , .. got this for free.
Wooden pallets can be used too and sometimes can be picked up for
free at your local businesses, wood and Styrofoam insulates good
and a good thing for northern climate, I also put about 1/2 inches thick sheet
of Styrofoam right under the void on the hive bottom board.

Konrad

I don't clear the snow around them and we had alot. The snow in our yard was above knee height most of the winter, and the hives are a couple hundred yards from the house, so I only wallowed out there about once a month to knock on the hives and hear if they were alive. The bottom entrances were often blocked with snow, but they all had top entrances.

I'm thinking something more stable is needed then just the two blocks to prevent the heaving. My hubby can get free plastic pallets from work.