Coming soon …but in short most probably the back connector in the back of the F key with the lever for A# key is not pushing A# down all the way. Try adding a piece of paper inbetween and gluing with a tiny bit of pen glue or shellac. The thinnest paper you can find is cigarette paper, about 0.001″. Regular print paper is about 0.004″ thick. Add little by little until they close together.