The guy at the LBS who worked on my bike tried a lot of different tigger shifters as well as the same rear derailleur shadow acera, regular acera and the only combo that worked was downgrading to altus. He had no clue why Acera did not work and I have a new Acera trigger shifters. All the other derailleurs and triggers had a problem that the gears only shifted up the cassette or down the cassette.