I confess not quite following you on that one, The fluid container is a separate container to that which is not displaying correctly.
I changed all the containers to
<div class="container">
removing fluid and centred text and the app connect display remains broken, the same issue. Only seems to happen with a bottom margin?
In this case all rows have mb-3 except the last which has mt-3. The latter displays correctly, those with mb-3 don’t
Should mention this is a node content page