I would say your mechanic finished the job and then realized he had forgotten the bump stops. There's an old trick to getting them to stick back up at the top if they ever fall down too- a bit of a pain, but it can be done. One has gone off with de pin in perfect condition. Im ready for the pain. P...

Thanks for the information Misha. I have a different but similar problem. When the gauge reches below 6 galons it stops measuring for a while. Then it goes up after a while I fuel it to 18 gallons and the it work well.
I´ll try dismatling and cleaning it. Thanks!