Precise vertical alignment of automation points

Hi - I am trying to vertically align automation points to move from one audio track to another at a precise point. When I zoom right in to do this (max zoom) in some cases Garageband allows me to do this but in other cases if you try to precisely vertically align the points they move back to their starting point and the alignment ends up being not precisely vertical. Does anyone know pl how to overcome this issue and be able to precisely align them? Thanks!!