I reported this issue a while back. Thought it might get fixed but not so far.
See: http://marmar.co50demo.com/#collections
The top photo is actually a column bg image (which allows it to cover the whole area no matter the width, whereas putting an image element there would cause it to shrink as the viewport narrows) while the two photos under are image elements. I need to get the top photo aligned properly so it’s left and right edges match the width of the bottom right photo. I went into Customize and set a CSS margin for the column but it has no effect unless marginless columns are turned off, but doing that makes what I’m trying to accomplish impossible.