Mongoose Pro Crossway 250 Step-through cycle

This Mongoose Pro Crossway 250 needed a service and the wheels trued and had an interesting problem with the front mech: It would change correctly on the stand but when on the road it would change from the high gear direct to the low gear but not from the middle gear to the low gear.

Despite repeated fettling this problem wouldn’t resolve itself. It got to the point when it would change smoothly on some roads but not others…In the end a new Shimano Acera front derailleur was fitted and the problem was solved, but it still bugs me when I can’t fix everything.