It does look like a bug; I have this filed in our system now to fix.
Specifically it only has an issue if the “Zoom contents” option is used in the group. Are you able to have the flexible layout behavior you want without this option?
Sorry, this has not yet been fixed but is categorized as a high priority for its correctness.
The workaround is to not use the Zoom Contents option or place the element with the viewport action outside of the group that has zoom contents enabled.