Images not sizing correctly in Grid

Hi, I’ve dropped my images into a Grid and set them 100% height 100% width fit:cover using a class.

However, my images are extending beyond my grid (coloured red so I can see it ) rather than being contained. Removing grid height does not cause it to collapse as expected.

What am I doing wrong please?

Here is my site Read-Only:

Sorry to anyone who view my link and wondered what I was talking about.

It works in Chrome but not in Safari. At least on my MacBook pro with Big Sur.