I have never seen a military bought/supplied float lose buoyancy. Never. Fall apart, turn to dust/powder, loose the magnets, wires loose in the plug, but never loose buoyancy. The contacts can stick in the metal rod. Or get burnt and not make contact correctly. So take it out, put it in a container of fuel or water. Test the contacts. leave it over night, and check it again. I would fabricate a way to keep the floats submerged.
Whats the NSN of the float. With that you can track down who supplied the float switch to the military. And maybe the company that produced it. They are not always the same.