I have read that Polonium does things like move against air currents or migrates within containers to (I think) different parts of the container. But I also read that a .5 gram chunk will reach 500 C. So what I wonder is, if one had a much smaller chunk, maybe salt-grain-sized, whether uneven heating (caused by unpredictable decay within the chunk) could create a sort of thrust with air molecules bouncing off of one side more energetically than the opposite side.
Or if it ionizes air, could not a small chunk being propelled by these ions? These ideas seem so obvious that it is hard to believe that the physicists who worked with the stuff would not have thought of them and therefore the behavior of $\rm Po$ would not be considered so mysterious.
One of the answers to this How warm are radioactive metals? is where I read of the high temperatures that $\rm Po$ reaches.