Great post Blue. Steel band is likely a 400 series stainles steel. 300 series stainless, which is used for flatware, knives, pots and pans, etc. is austenetic stainless and is much more corrosion resistant, but is not magnetic at all. 400 series which is ferritic has some iron and therefore will corrode over time. Alloys like 409 (mufflers, tail pipes, Cats, etc.
430, 439, et al) are "slightly magnetic" and have decent magnetic properties for use as a sensor trigger. My plastic bobber must have separated from the float and possibly a re-bleed is necessary-why I'm not sure after all this time, but hey-if it works- who cares!
That would be the combo that explains my behavior. Sensor is still working. Bobber is just useless as an indicator. Must use sight and watch for DIC msgs.