Hello!
Thanks for reaching out! I see you managed to fix the height via custom CSS on your website.
To make each button consistent, you should be able to put the padding settings on the "button group" level instead of on each button that is inside the button group. You can click where you see below in my screenshot.

And set the padding to similar values to what I show below. It looks like that will make your button heights 60px for both buttons.

After making the changes above, you can revert to the default padding settings for each button inside the group by clicking it and then click the arrow icon you see here:

Please let me know if you have any questions. I didn't want to mess with your settings since you have it working right now, so it's up to you if you'd like to try it so you can avoid using custom CSS that way.
Cheers,
Tony