I have this bug happening in my document too. It's not just the baseline that is shifting, but the whole button.
Having taken a look through the code after exporting my document, it looks like the button object is getting shifted out of place by 3 pixels both horizontally and vertically.
Pretty easy to fix in the code, or by adjusting the buttons in your document to compensate before exporting, but if there is a better fix I'd love to hear it to save some time.