Neutral switch for 1981 900 SS

[jsey]

So my neutral light stopped working so I went looking under the cover. Switch was total frozen and inoperative. Found a new one and have run into the most confounding thing. The old one measures .230 so its 6 mm and the thread is either .80 or .75. The new one measures exactly .250 so 1/4' and what looks like 32 TPI. The small holder is tapped 6mm x.75. I have a 1/4'-32 tap but when I do a test on a piece of aluminum its pretty sloppy. Why would Ducati have made a switch with a 1/4' thread?