It seems that the responsiveness option to “collapse margins when container width is ≤ x” is not available when the container is a repeating group…
My workaround is to contain the desired element(s) in another group that is the width of the repeating group, but is the child of the repeating group.
With the element’s first parent now being a normal group (whose parent in turn is the repeating group), the option to collapse margins of the element becomes available again, but I don’t understand why this step is necessary.
Am I missing something on why this limitation might make sense? Or is this a bug?