After taking a look, I can see that your main groups tend to each have different heights, which is why you have the extra space at the bottom.
I made a slight change to the forum app page I posted for you earlier. https://bubble.io/page?type=page&name=native-app-page-height&id=forumapp3&tab=tabs-1
This time, I made the main group the height of the entire page and put the collapsible group inside the main group at the bottom. If you follow this method and insert a collapsible group at the bottom of each of your main groups, the page should be the correct height no matter what.