We had a bunch of trouble with the FD on my wife's Fuji when we bought it. The mechanic would get it adjusted on the stand but in the real world, my wife couldn't get the chain onto the big ring. I'd adjust it during the ride to get it to shift and then she'd get the grinding. Took it in several times but always came back with same issue.
One day we were on a ride and I could see my wife was frustrated. We were only a few miles from the LBS so we rode over there. They adjusted, she test rode, not fixed. They readjusted, she test rode, still not fixed. This went on for a while and my wife was ready to accept that it was operator error but I encouraged her that it wasn't her it was a mechanical issue.
After many more rounds of this, they finally replaced the FD and it has worked perfectly every since. Never give up!