Fuel gauge reading incorrectly

I guess I'm just the lone ranger. I've used several Spectra sending units through the years, two very recently and none have read wrong. That's none. They are made in Canada. I've installed them in Mopars, General Motors products and Fords and every single one of them read correctly. The only thing I had to do to one, my Ford truck was adjust the float arm just a little. Other than that, they were install and go.