When working in the glyph window, the view is centralized around the current selection. So when going from one master to another the baseline jumps automatically. Is there a way to deactivate this ? And to keep the baseline on the same vertical position.
And in the preview window size changes when going from one master to another.
The preview window uses the vertical metrics to scale the outlines. If those need to be so different, you can use Preview Ascender and Preview Descender custom parameters to use the same scale in all masters.